1. Message to beginners
2. Intro
3. Major use case: Parent and Child CGridViews on single view
4. Another use case: Child-grid in create and update views

Message to beginners ¶

This wiki is a step-by-step example explaining how the controller, model and the view's CGridView work together. It explains simple things - as well as more complex things that you will anyway quickly have to know. So, even if you don't use dynamic gridviews, take a morning off and thoroughly work through this tutorial. It should save you lots of struggling.

Intro ¶

Forgive me for maybe “over-explaining” things a bit, which results in such a lengthy wiki, but the idea is to also cater for beginners. So people who are in a hurry only need to read the sections on 'The Process (in short)', the 'Views', the 'RoleController' and the 'Ajax' methods.

Many desktop programmers are used to having dynamic forms, where clicking on a record in a parent sub-form, updates another sub-form with the child records. While having many levels of nested sub-forms in a single view might not be such a good idea for a web application, I thought doing it one level deep might be interesting and useful. But, instead of sub-forms I used CGridViews.

Major use case: Parent and Child CGridViews on single view ¶

The Process (in short) ¶

If you want to retrieve the child records for a certain parent record, then you would NORMALLY just "read" one of the parent model's relations to the child model. This is called "Relational Query" in the Yii documentation.

However, in this example, we do not simply want to display the child records. No, we need much more. We need to be able to manipulate (sort/search/page and maybe even view/update/delete) the child records in their own CGridView. But to do all this with the child records in their own CGridView, they will need their own dataprovider.

So we do this by getting the child records DIRECTLY (not via relation query) from their own model, where their own dataprovider can be generated.

So (in short) the process works like this:

1. The user clicks on a parent record in the parent-gridview.

2. The parent record's primary key (PK) is sent from the view (client) to the controller (server) - via our own Ajax function (client).

3. The controller renders the child-gridview and also passes it the PK. Render means the following: While being generated (on the server), the child-gridview passes the PK to its own child-model's search() function, where it is incorporated as a filter for retrieving the relevant child records and storing them in a new child-dataprovider. The child-gridview uses this child-dataprovider for its rows. The child-gridview is then send to the client.

4. On the client, our Ajax function receives the new child-gridview from the server and replaces the old child-gridview in the browser.

So here we go! *****

Database ¶

In the database I have a classic many_many relation, which is broken/represented by a junction table. The two outer tables are called "cap_role" (PK: role_id) and "cap_permission" (PK: permission_id). The junction-table in the middle is called cap_role_permission (PK: rolepermission_id) (Unique: role_id, permissionid). (Tables are prefixed by "cap".)

The idea is that you link permissions to roles (users will later be given roles). So obviously, a role could have many permissions, and a permission could also be assigned to many roles.

(Yii calls the direct relation between the two outer tables - with the junction table between them - a many_many relation. But you still must have the junction table in the middle! So there is no real many_many relation in the database.

Yii's many_many relation is thus simply a way of using one of the outer table’s models, and then getting data directly from the other outer table – without having to work “through” the junction table (like in sql). But in the background Yii still works through the junction table, so you still need it in the database. That is also why you will have to specify the cap_role_permission table, as part of the many_many relation between the outer tables.

The advantage of many_many relations is that it saves memory, because Yii don't need to create additional model instances for the junction table's records during a query.

Having said that, this wiki was updated in May 2012 to get the child records directly from their own model - without working through the many_many relation any more.)

Overview ¶

I used the views/role/admin view for al the action. The parent-gridview displays the default Role models. The child-gridview uses a different model - the RolePermission model - to display the permission_id of the relevant cap_role_permission records. In addition, the RolePermission model uses its relation with the Permission model (normal "Relational Query") to also display the permission_desc fields of the related cap_permission records.

Views ¶

My views\role\admin.php view:

<h1>Manage Roles</h1>

<?php echo CHtml::link('Advanced Search','#',array('class'=>'search-button')); ?>
<div class="search-form" style="display:none">
	<?php $this->renderPartial('_search',array(
		'model'=>$parent_model,
	)); ?>
</div><!-- search-form -->

<div id="parentView">
	<?php
		/*For the above "Advanced Search" function to work, keep the gii
		generated id for the parent CGridView. 
		In this case it is "role-grid". 
		If you do want to change it to something else - like parent-grid -
		then also change the name in the javascript 'search' function, that
		is normally located just above the "Advanced Search" function.

		Add the line: 'ajaxUpdate' => 'child-grid', to the parent
		CGridView (role-grid). This ensures that the child-grid is also
		refreshed when the role-grid is sorted/filtered/paged via the 
		build-in Yii ajax.

		How does it work?: Ajax is suppose to update only certain sections
		of a view (on the client), with data specific to that section,
		which is obtained from the controller and/or model (on the server).
		
		So ajax is about speed, because you don't need to wait for the
		entire page's data each time you want to update a section.
		
		However, Yii's ajax when doing gridview sorting, filtering and
		pagination works differently. In these cases, the entire view is
		still rendered to the client, but Yii then only refreshes the
		gridview and ignores the rest of the received data. For this
		reason, the default gii generated actionAdmin has only one
		render function, which renders the entire view - regardless of
		whether the event refreshes the whole page or actually needed only
		a section of the view. (This way of treating ajax, only pertains
		to CGridViews in gii generated controllers. You could change it if
		you want - since gii is only intended to give you a platform to
		start from. But I'm also sure it will be improved in future Yii
		releases.)
		
		In our example, when the role-grid gets sorted, 'ajaxUpdate' => 
		'child-grid' tells Yii to also extract the child-grid's data from
		the received view and to update it together with the role-grid.
		(If you have dynamic headings in the childView, or other data that
		also needs to be updated, then use 'ajaxUpdate' => 'childView'.
		This will update the entire childview with all its headings, as well
		as the child-grid inside the childView.)
		Please note that 'ajaxUpdate' is part of the build-in Yii ajax.
		It is NOT part of our own custom ajax function (GROUP B 3.1 in the
		actionAdmin of the RoleController), which we will use to only
		retrieve data for the child-grid, and update only the child-grid,
		after a row in the role-grid was clicked.*/
		$this->widget('zii.widgets.grid.CGridView', array(
			'id'=>'role-grid',
			'dataProvider'=>$parent_model->search(),
			'filter'=>$parent_model,
			'columns'=>array(
				'role_id',
				'role_desc',
				array(
					'class'=>'CButtonColumn',
				),
			),
			'ajaxUpdate' => 'childView', //or 'ajaxUpdate' => 'child-grid'
		));
	?>
</div>

<!-- Use this paragraph to display the loading.gif icon above the Child Gridview,
while waiting for the ajax response -->
<p id="loadingPic"></br></p>

<!-- The childView <div>, renders the _child form, which contains the Child Gridview.
The ajax response will replace/update the whole <div> and not just the gridview. -->
<div id="childView">
	<?php
		$this->renderPartial('_child', array(
		'child_model' => $child_model, 
		'parentID' => $parentID, 
		))
	?>
</div>

<?php
	/*Load the javascript file that contains our own ajax function*/
	$path = Yii::app()->baseUrl.'/js/customFunctions.js';
	Yii::app()->clientScript->registerScriptFile($path,
	CClientScript::POS_END);
?>

The following _child.php form contains the Child CGridView. The gridview receives a dataprovider using the searchIncludingPermissions($parentID) function in the RolePermission model. The same function is used for filtering and sorting. (Note that the controller sets $child_model to refer to the RolePermission model and not to the default Role model).

Under the gridview’s columns we have the RolePermission model’s permission_id and the related Permission model’s permission_desc. Since permission_desc is a related field with sorting and filtering enabled, it should be specified in this special way.

Note that the buttons in this gridview have been customized to use the child records' controller (RolePermissionController) and not the default RoleController. If you think this will confuse the user, take them out. However, I think it could be a lovely feature if you have, for example, school classes in the parent-gridview and students in the child-gridview. By clicking on a class in the parent-gridview, the child-gridview displays a list of the students in that class and you can immediately update a student's details by clicking the update button in the child-gridview. Having said that, I would only have 'update' buttons in the child-gridview, otherwise it could get confusing. You can also link these buttons to the PermissionController if required.

To only show the 'update' button, change the template to the following:'template'=>'{update}',

You can read more about this here: CButtonColumn

The first paragraph uses the subsectionheading CSS class. You can obviously change that to your own CCS class.

<p id="subsectionheading">Permissions linked to the above selected Role</p>
<div class="hint">(Please note: If no Role is selected, the Permissions of the top-most Role are displayed.)</div>

<?php
	$this->widget('zii.widgets.grid.CGridView', array(
	'id'=>'child-grid',
	'dataProvider'=>$child_model->searchIncludingPermissions($parentID),
	'filter'=>$child_model,
	'columns'=>array(
		'permission_id',
		array(
			'name'=>'permission_desc_param',
			'value'=>'($data->relPermission)?$data->
				relPermission->permission_desc:""', /* Test for
				empty related fields not to crash the program */
			'header'=>'Permission Description',
			'filter' => CHtml::activeTextField($child_model,
			'permission_desc_param'),
		),
		array(
			'class'=>'CButtonColumn',
			'template'=>'{view}{update}{delete}',
			'viewButtonUrl' => 'array("rolepermission/view",
			"id"=>$data->permission_id)',
			'updateButtonUrl' => 'array("rolepermission/update",
			"id"=>$data->permission_id)',
			'deleteButtonUrl' => 'array("rolepermission/delete",
			"id"=>$data->permission_id)',
		),
	),
));
?>

CSS ¶

The CSS for the paragraph displaying the loading.gif icon (this is toggled in our ajax function). You can find a loading.gif file in your local Yii installation:

.loadGIF {
	background: black url(/main/sub/css/images/general/loading.gif) left center no-repeat ;
}

The RoleController ¶

To understand what is happening in the RolePermission model, you first have to know what the controller is doing. Hence my lengthy comments:

The Parent CGridView in the admin view is called 'role-grid', which is Yii's default id for the CGridView displaying the Role models. The Child CGridView is called 'child-grid'.

When a row in role-grid is clicked, our custom ajax function extracts the row's primary key and stores it in a variable called parentID, which is then passed to this actionAdmin.

However, this actionAdmin is called by quite a few other events/functions (done by Yii) as well, but not all of them also pass the stored parentID to actionAdmin.

Thus, I have divided the events into Groups A and B:

GROUP A (Events that DO NOT pass parentID to actionAdmin):

At all times:
1.1	Initial rendering/refreshing of the 'admin' form,
	displaying both role-grid and child-grid;
1.2	role-grid sorting (Yii ajax),
1.3	role-grid filtering (Yii ajax),
1.4	role-grid pagination (Yii ajax).
		
Only BEFORE any role-grid data row was clicked:
2.1	child-grid sorting (Yii ajax),
2.2	child-grid filtering (Yii ajax),
2.3	child-grid pagination (Yii ajax).

GROUP B (Events that DO pass parentID to actionAdmin):

At all times:
3.1	role-grid clicking (own custom ajax function).

Starting only AFTER any role-grid row was clicked:
4.1	child-grid sorting (Yii ajax),
4.2	child-grid filtering (Yii ajax),
4.3	child-grid pagination (Yii ajax).

Note that 4.1 - 4.3 are the same events as 2.1 - 2.3, but they only start passing the parentID after a data row in the role-grid was clicked. Again, these are all Yii events and we don't have control over how they are functioning (unless you want to change the Yii files). So, we only have control over what 3.1 is doing, but for the rest - we have to cater for their behaviors.

*When actionAdmin is used by any of the above events, we don’t know which event it is. We also don’t know if the user has entered any text (filtering parameters) in the gridview’s “search” textfields, which should be used to filter the column’s data.

To prepare for all these possibilities, gii generates the standard actionAdmin functions to do more or less the following:

Process1: Create a single model instance (let's call it the filtering-model) and put it in the 'search' scenario. (It only puts the model in the 'search' scenario. It does not execute the model's search() function yet. More about scenarios in the RolePermission model.)

Empty the model from all default values, because we are going to use this model to store the user's filtering criteria as well as our own filtering criteria. So we don't want any default values to interfere with the filtering.

(In this example the filtering-models are called $parent_model and $child_model respectively.)

Process2: Test if the event currently using actionAdmin, passed any filtering parameters that the user might have entered. If such parameters are found, store them in the newly created filtering-model.

Process3: Render the view and pass it the filtering-model - which now contains the user's filtering parameters, but does not form part of the data records for the gridview.

Process4: The view renders the gridview,

Process5: which executes the filtering-model's search() function,

Process6: which incorporates the filtering-model's parameters into a dataprovider

Process7: and returns the dataprovider to the gridview to use for data records.

So if we use "$this->" in the model's search() function, we are actually referring to the filtering-model instance, which contains the user's filtering parameters and which was passed to the view by the controller.

And that is exactly why - in the search() function - we can have a statement like:

$criteria->compare('field1', $parent_model->field1, false);

This statement instructs the dataprovider to only include records where

field1 = the value of field1 in the filtering-model ($parent_model).

So if the user enters a value in field1 on the CgridView, that value will end up in the filtering-model (Process2 in the controller), which is used in the model's search() function (executed by CGridView in the view - Process5) to filter the records of the new dataprovider (Process6), which will update the CGridView's data rows (Process7).

This wiki's actionAdmin has a few additional tests/processes and it works with two models, but the basic functioning is the same.

It is also important to know that, besides from the user's filtering parameters that we store in the filtering-model, we can also store our own values in this model instance, which we can then use to further influence the filtering of records in the dataprovider. We can even declare additional variables in the model - or pass additional parameters directly to the model's search() function - to use as filtering parameters.

Examples of such additional parameters in this wiki are:

1. the record id of a clicked row in the parent GridView, PASSED in a variable called parentID, and used to filter the child records;

2. special variables DECLARED in the model, used to filter the gridview on fields from RELATED records (fields not automatically part of our filtering-model).

public function actionAdmin()
	{
		/* Process1:
		Create a single filtering-model instance (placing it in the
		'search' scenario), which will hold the role-grid's filtering
		parameters entered by the user.*/
		$parent_model = new Role('search');
		
		/* Empty the newly created filtering-model to clear all
		default parameters.*/
		$parent_model->unsetAttributes();
		
		/* Process2:
		Test if the event that is currently calling this action, passed
		any filtering parameters that the user might have entered in the
		role-grid.
		If true, store these parameters in the newly created filtering-model
		instance. */
		if(isset($_GET['Role']))
			$parent_model->attributes=$_GET['Role'];
		
		/* Test if the event that is currently using this action, is from
		Group A or B */
		if(!isset($_GET['parentID'])){
			/* The event using this action now, is from Group A:*/
			$group = "A";
			
			/*The parentID was not passed to the controller and since
			we do not know which event is currently using actionAdmin
			(could be refreshing, sorting, paging, etc.), we do not
			know what records to display in the child-grid.
			So we need to find out which record will next be displayed
			at the top of the role-grid - considering all the
			filtering parameters (stored in our single parent-model
			instance) that we might/might not have received	from the
			event.
			
			Then we need to extract that top record's PK so that we
			can pass it to the view	to use it to generate the child-
			gridview's dataprovider.
			
			So the easiest way of doing this is to copy-cat the
			model's search() function (which will be used to generate
			the role-grid's real dataprovider).
			
			I thus created a temporary dataprovider in the controller,
			in which I incorporated all the filtering parameters
			received from the event - if any.
			
			NOTE: This way of obtaining the role-grid's first 
			record-to-be, could most probably be done in another way.
			For example: 
			I tried to extract the first record from the real 
			dataprovider after it was generated in the model 
			(Process6). But the problem is that you cannot then pass
			control back to the controller to continue testing how the
			child-gridview should be generated, because control has 
			then been passed to Process7, which renders the views.
			
			And if you want the view (in Process7) to render the child-
			gridview via another ajax function, that would probably
			result in a further round trip to the server. Creating
			a temporary dataprovider in the controller is much faster.
			
			And if you store the PK in the model or in the session 
			state during Process6, you still have to wait until one of 
			the events in Process7 calls the controller and passes it 
			the PK together with any new filtering criteria. However, 
			by that time the PK is OLD NEWS, because the new event 
			would normally result in a different first role-grid 
			record being needed.
			
			So for these reasons, I obtain the first record-to-be 
			directly in the controller, before the child-gridview is 
			generated. 
			
			(Note: I tried to limit the records in this dataprovider 
			by adding 'pagination' => array('pageSize' => 1,), but 
			since pagination then behaves differently from that
			of the real dataprovider in the model, the record-to-be
			would differ, resulting in the child-grid displaying the
			wrong records. So this dataprovider should be identical to
			that in the model's search() function.) */
			$criteria=new CDbCriteria;

			$criteria->compare('role_id',$parent_model->role_id,true);
			$criteria->compare('role_desc',
			$parent_model->role_desc,true);

			$dataProvider = new CActiveDataProvider('Role', 
				array(
					'criteria'=>$criteria,
				));
			
			/* Test if the dataProvider found any data (filtering 
				parameters might have excluded all records)*/
			If (count($dataProvider->getData()) > 0) {
				/* Extract the first model from the dataprovider */
				$first_model=$dataProvider->getData();
						
				/* Extract the record's PK, to be used to generate 
				the child-gridview's data records.*/
				$parentID = $first_model[0]->role_id;
			}
			else{
				/* Set $parentID to 0, to return an empty child-
				grid.*/
				$parentID = 0;
			}
		}
		else{
			/* The event using this action, is from Group B: */
			$group = "B";
			
			/* Get the parentID, which the event passed to this 
			action.*/
			$parentID = $_GET['parentID'];
		}

		/* Process1:
		Create another filtering-model instance which will hold the
		child-grid's filtering parameters entered by the user.
		Put this model in the searchIncludingPermissions scenario. */
		$child_model = new 
			RolePermission("searchIncludingPermissions");
		
		/* Empty the newly created filtering-model to clear all 
		default parameters.*/
		$child_model->unsetAttributes();
		
		/*If you later need to change this model's scenario for whatever
		reason, you can do it like this. (More details on scenarios in the
		RolePermission model.) */
		$child_model->scenario = 'anotherScenario';
		
		/* Process2:
		Test if the event that is currently calling this action, passed 
		any filtering parameters that the user might have entered in the 
		child-grid.
		If true, store these parameters in the newly created 
		filtering-model instance. */
		if(isset($_GET['RolePermission']))
			$child_model->attributes=$_GET['RolePermission'];

		/* Process3:
		Test if the event that is currently using this action, is from 
		Group A or B */
		if($group == "A"){
			/* GROUP A:		
			Render the 'admin' form while passing it $parentID and
			both filtering-model instances (containing the user's
			and our own additional filtering parameters - if any).
			(Remember, the form's gridviews use the Role->search() and
			RolePermission->searchIncludingPermissions(parentID) 
			functions to create their own dataproviders.
			These functions will incorporate $parentID and any 
			received filtering parameters contained in the two
			filtering-models.
			
			Note that the whole admin view is rendered (default gii
 			way of doing it), even if the event currently using this
			action might be	one of the Yii ajax functions (GROUP A, 
			1.2 - 2.3), which would normally only require a section of 
			the view. See the role-grid in the admin.php view for more 
			information on why the whole admin view is rendered. */
			$this->render('admin',array(
				'parent_model'=>$parent_model,
				'child_model'=>$child_model,
				'parentID' => $parentID,
			));
		}
		else{
			/* GROUP B:	
			Render only the '_child' form while passing it $parentID 
			and the single filtering-model (child-model) instance.

			The form's gridview will use the
			RolePermission->searchIncludingPermissions($parentID)
			function to create it's own dataprovider.
			This function will also incorporate $parentID and any 
			received filtering parameters contained	in the single 
			child-model instance.*/
			$this->renderPartial('_child', array(
				'child_model'=>$child_model,
				'parentID' => $parentID,
			));
		}
	}

Models ¶

There is nothing special about the Role model, which will be used as default model for the role-grid. So you can use the standard gii generated Role model.

There is no need to use the Permission model (for the cap_permission table) since I'm directly obtaining the permission_desc field by using the relPermission relation in the RolePermission model.

The RolePermission model looks like this:

<?php

class RolePermission extends CActiveRecord
{
	/* This variable is used to store the parameters enetered by the user for
	filtering the child-gridview's Permission Description column*/
	public $permission_desc_param;

	/**
	 * Returns the static model of the specified AR class.
	 * @param string $className active record class name.
	 * @return RolePermission the static model class
	 */
	public static function model($className=__CLASS__)
	{
		return parent::model($className);
	}

	/**
	 * @return string the associated database table name
	 */
	public function tableName()
	{
		return '{{role_permission}}';
	}

	/**
	 * @return array validation rules for model attributes.
	 */
	public function rules()
	{
		// NOTE: you should only define rules for those attributes that
		// will receive user inputs.
		return array(
			array('role_id, permission_id',	'required'),
			array('role_id, permission_id',	'length', 'max'=>10),
			// The following rule is used by search().
			// Please remove those attributes that should not be 
			searched.
			array('role_id, permission_id,
				permission_desc_param', 'safe', 'on'=>'search, 
				searchIncludingPermissions'),
		);
	}

	/**
	 * @return array relational rules.
	 */
	public function relations()
	{
		// NOTE: you may need to adjust the relation name and the related
		// class name for the relations automatically generated below.
		return array(
			'relRole' => array(self::BELONGS_TO, 'Role', 'role_id'),
			'relPermission' => array(self::BELONGS_TO, 'Permission', 
			'permission_id'),
		);
	}

	/**
	 * @return array customized attribute labels (name=>label)
	 */
	public function attributeLabels()
	{
		return array(
			'rolepermission_id' => 'Rolepermission ID',
			'role_id' => 'Role ID',
			'permission_id' => 'Permission ID',
			'system_record' => 'System Record',
		);
	}

	/**
	 * Retrieves a list of models based on the current search/filter
	conditions.
	 * @return CActiveDataProvider the data provider that can return the 
	models based on the search/filter conditions.
	 */
	public function search()
	{
		// Warning: Please modify the following code to remove attributes
		// that should not be searched.
		$criteria=new CDbCriteria;
		$criteria->compare('rolepermission_id',
			$this->rolepermission_id,true);
		$criteria->compare('role_id',$this->role_id,true);
		$criteria->compare('permission_id',$this->permission_id,true);
		
		return new CActiveDataProvider($this, array(
			'criteria'=>$criteria,
		));
	}
	
	public function searchIncludingPermissions($parentID)
	{
		/* This function creates a dataprovider with RolePermission
		models, based on the parameters received in the filtering-model.
		It also includes related Permission models, obtained via the
		relPermission relation. */
		$criteria=new CDbCriteria;
		$criteria->with=array('relPermission');
		$criteria->together = true;
	
		
		/* filter on role-grid PK ($parentID) received from the 
		controller*/
		$criteria->compare('t.role_id',$parentID,false); 
		
		/* Filter on default Model's column if user entered parameter*/
		$criteria->compare('t.permission_id',$this->permission_id,true);
		
		/* Filter on related Model's column if user entered parameter*/
		$criteria->compare('relPermission.permission_desc',
			$this->permission_desc_param,true);
		
		/* Sort on related Model's columns */
		$sort = new CSort;
		$sort->attributes = array(
			'permission_desc_param' => array(
			'asc' => 'permission_desc',
			'desc' => 'permission_desc DESC',
			), '*', /* Treat all other columns normally */
		);
		/* End: Sort on related Model's columns */
		
		return new CActiveDataProvider($this, array(
			'criteria'=>$criteria,
			'sort'=>$sort, /* Needed for sort */
		));
	}
}

So what is happening in this model?

Normally CgridViews get their data records by using the model’s search() function, which returns a dataprovider.

I did not want to amend the model’s search() function, because other controllers need to use it as well. So I created a new function called searchIncludingPermissions(). This function performs the same basic tasks as the search() function, but it also:

1. includes the related permission records via the model's relPermission relation;

2. filters the child records on the role-grid's PK ($parentID received from the controller);

3. filters the child records on the user entered parameters (received from the controller in the single child-model instance),

4. takes care of child-gridview sorting and pagination AFTER a row in role-grid was clicked.

The searchIncludingPermissions() function receives the $parentID parameter from the child-gridview, after it was passed to the view from the controller.

The $criteria->compare('t.role_id', $parentID,false) statement filters the child records - comparing their role_id to $parentID - only allowing an exact match (false). This filtering occurs regardless of whether the user included additional filtering parameters.

The next two compare statements filter the user's filtering parameters – if any:

$criteria->compare('t.permission_id',$this->permission_id,true);

“$this” refers to the single filtering-model instance received from the view, so $this->permission_id will contain any filtering parameters that the user might have entered in the child-gridview’s permission_id column. So the above statement compares the dataprovider (to be created) records with the filtering-model instance received from the controller.

But there is a problem with the next compare statement: The models to be created in the real dataprovider will have the following structure:

• rolepermission_id

• role_id

• permission_id

• relPermission.permission_id

• relPermission.permission_desc

However, the filtering-model instance does not have the same structure. It does not contain fields to store the user’s filter parameters for the RELATED fields (due to lazy loading):

• rolepermission_id

• role_id

• permission_id

• relPermission

Therefore you can’t write the last compare statement like this:

$criteria->compare('relPermission.permission_desc',$this->relPermission->permission_desc,true);

So the answer to this problem is to create a separate public variable in the model and use it to store the user’s filter parameter for the related column. This public variable is declared at the top of the model, called permission_desc_param.

Now we can use it in the compare statement:

$criteria->compare('relPermission.permission_desc',$this->permission_desc_param,true);

You can read more about this solution here: Searching and sorting by related model

The permission_desc_param variable is also used in the child-gridview’s column filter (see the child-grid in the _child.php view).

permission_desc_param also needs to be included in this model's safe rule. This will ensure that it will also be assigned its correct value during Process2 in the controller - without us needing to specifically pay extra attention to it.

Important: For the safe rule to also be applied to the searchIncludingPermissions function, the rule must be amended to also work for the "searchIncludingPermissions" scenario, and not just for the "search" scenario. array('..., permission_desc_param', 'safe', 'on'=>'search, searchIncludingPermissions') You will remember that the controller placed the child filtering-model instance in the searchIncludingPermissions scenario.

Scenarios are simply used to enforce different model rules at different times. You can read more about scenarios here: Model rules validation

Our own Ajax (passing CGridView data to the controller) ¶

1. Our own Ajax - Method-1 ¶

(Constantly displaying the child-records)

Different Javascript, Ajax and Jquery options: I first used the role-grid's own selectionChanged event to update the child-grid, but that caused problems when the user clicked the same row twice, since the second click deselected the same row that has just been selected by the first click. This deselecting of the row caused $.fn.yiiGridView.getSelection() not to be able to get the PK of the clicked row, which meant that I could not constantly get the correct PK to constantly display the child-grid. (This could be a good option in some cases. See "Our own Ajax - Method-2" below.)

I then used pure ajax with a function that checked the readyState from the server’s response after the ajax call. However, the function worked fine in Firefox but not in Internet Explorer 8.

After that, I used jquery's $('#role-grid table tbody tr').click(function(){. This function binds a click event handler on all data-rows in the role-grid. However, whenever the gridview was paged, these rows - and their assigned event handlers - no longer existed. This behavior results in many questions on the forum about things not working correctly after CGridView or CListView was paged. Also see my example in one of these posts here.

I thus moved to using jquery's Event Delegation: It binds an "on()" event handler to the parentView div, which is the role-grid's parent.

This handler first watched for click events bubbling up when the user clicks one of the gridview's data rows. However, the rows also fired a click event if the user clicked one of the buttons in the row - which is not what I wanted.

So finally, I changed the script to check for clicking events coming from a row's columns (except the button-column). The first line thus binds an event handler on the outer parent - the parentView div. This handler looks for click-events bubbling up from any data-row (tbody) columns (td) that are not of class button-column (this is our own ajax in the separately loaded javascript file - called customFunctions.js).

$('#parentView').on("click", "table tbody td:not(td:.button-column)", function(event){

	try{
		/*Extract the Primary Key from the CGridView's clicked row.
		"this" is the CGridView's clicked column or <td>.
		Go up one parent - which gives you the row.
		Go down to child(1) - which gives you the first column,
			containing the row's PK. */
		var gridRowPK = $(this).parent().children(':nth-child(1)').text();
		
		/*Display the loading.gif file via jquery and CSS*/
		$("#loadingPic").addClass("loadGIF");
				
		/* Call the Ajax function to update the Child CGridView via the
 		controller’s actionAdmin.*/
		
		var request = $.ajax({ 
		  url: "Admin",
		  type: "GET",
		  cache: false,
		  data: {parentID : gridRowPK},
		  dataType: "html" 
		});

		/* Url Problems: 
		If you receive 404 errors about the request not finding the
		correct page or 'request failed' etc., then the above url is 
		probably not formatting	correctly. (Use Firebug to see if the
		generated url contains both the controller and the action names.)
		However, this error sometimes results from code in a totally 
		different location.
		
		For example: I got this error when I had the following line in my 
		urlManager in the config/main.php file:

		'<controller:\w+>' =>'<controller>/admin', //if no action is 
		provided, use actionAdmin

		When the user clicks on my CHtml::link to go to my actionAdmin 
		for the first time, the above line caused CHtml::link to not 
		include the action's name in the url in the browser's address bar.

		I guess the ajax-request uses the same url in the address bar to
		generate its own url.
		So make sure your url in the browser's address bar contains both 
		the controller and action names.*/

		request.done(function(response) { 
			try{
				/*since you are updating innerHTML, make sure the
				received data does not contain any javascript - 
				for security reasons*/
				if (response.indexOf('<script') == -1){
					/*update the view with the data received 
					from the server*/		
			document.getElementById('childView').innerHTML = response;
				}
				else {
					throw new Error('Invalid Javascript in 
					Response - possible hacking!');
				}
			}
			catch (ex){
				alert(ex.message); /*** Send this to the server 
				for logging when in production ***/
			}
			finally{
				/*Remove the loading.gif file via jquery and CSS*/
				$("#loadingPic").removeClass("loadGIF");
					
				/*clear the ajax object after use*/
				request = null;
			}
		});
		 
		request.fail(function(jqXHR, textStatus) {
			try{
				throw new Error('Request failed: ' + textStatus );
			}
			catch (ex){
				alert(ex.message); /*** Send this to the server 
				for logging when in production ***/
			}
			finally{
				/*Remove the loading.gif file via jquery and CSS*/
				$("#loadingPic").removeClass("loadGIF");
					
				/*clear the ajax object after use*/
				request = null;
			}
		});
	}
	catch (ex){
		alert(ex.message); /*** Send this to the server for logging when 
		in production ***/
	}
});

2. Our own Ajax - Method-2 ¶

(Displaying the child-records only when parent-row is clicked)

As time goes by, you tend to add more complex features to your gridviews. A feature that I added, enables the user to select the number of rows the gridview should display (by adding a header with a dropdownlist to the CButtonColumn; and then getting the dataprovider to incorporate this dropdownlist's value into the pageSize.)

Obviously these kind of functionalities make it more difficult to 'calculate' the first record-to-be in the controller. And if you add even more complexity - such as displaying your gridviews in different CJuiTabs and in separate dialogs - then the task of getting the first record-to-be in the controller, could become quite difficult.

So, in these cases I made peace with the idea that the child-gridview can not constantly display the child records. It only displays the child records after the user clicks a row in the parent-drigview. For all other GROUP-A events, the child-gridview is empty.

This is not all bad. The advantage of this is that we can now use $.fn.yiiGridView.getSelection() to get the parent-gridview's PK. So we are not forced any more to include the PK in the gridview's first column, because $.fn.yiiGridView.getSelection() finds the PK regardless of whether it is included in the gridview or not.

Another advantage is that we don't need to 'calculate' the first record-to-be in the controller any more, since the child-gridview is now only displayed with GROUP-B events.

We also don't need JQuery's Event Delegation in our Ajax any more, because after the user clicked a row, the parent-gridview can simply run our Ajax function by itself.

So the controller's GROUP-A and GROUP-B testing section can become as simple as this:

if(!isset($_GET['parentID'])){
	$group = "A";
	$parentID = 0; //Child-gridview will have no records
}
else{
	$group = "B";
	$parentID = $_GET['parentID'];
}

The parent-gridview can now do the job of calling our Ajax function (Jquery's Event Delegation is not performing this job any more):

$this->widget('zii.widgets.grid.CGridView', array(
		'id'=>'role-grid',
		'dataProvider'=>$parent_model->search(),
		'filter'=>$parent_model,
		'ajaxUpdate' => 'childView',    //or 'ajaxUpdate' => 'child-grid'
		'afterAjaxUpdate' => "updateChild",  // new code
		'selectionChanged'=> "updateChild",  // new code
		'columns'=>array(...

updateChild is the new name for our own custom Ajax function. Note that the Event Delegation has been removed from the first line:

function updateChild(id, options)
{
	try{
		/*	Extract the Primary Key from the CGridView's clicked row */
		var myPK = parseInt($.fn.yiiGridView.getSelection(id));
		
		/* If $.fn.yiiGridView.getSelection(id) can not find PK, then return. */
		if(isNaN(myPK)){
			return;
		};
		
		/*Display the loading.gif file via jquery and CSS*/
		$("#loadingPic").addClass("loadGIF");
				
		/* Call the Ajax function to update the Child CGridView via the
		 controller’s actionAdmin */
		var request = $.ajax({ 
		  url: "Admin",
		  type: "GET",
		  cache: false,
		  data: {parentID : myPK},
		  dataType: "html" 
		});
		
		/* See "Url Problems" at this same location in 
		 "Our own Ajax - Method-1".*/

		request.done(function(response) { 
			try{
				/*since you are updating innerHTML, make sure the
				received data does not contain any javascript - for
				security reasons*/
				if (response.indexOf('<script') == -1){
					/*update the view with the data received
					 from the server*/
					document.getElementById('childDiv').innerHTML = response;
				}
				else {
					throw new Error('Invalid Javascript in Response - possible hacking!');
				}
			}
			catch (ex){
				alert(ex.message); /*** Send this to the server for
				 logging when in production ***/
			}
			finally{
				/*Remove the loading.gif file via jquery and CSS*/
				$("#loadingPic").removeClass("loadGIF");
					
				/*clear the ajax object after use*/
				request = null;
			}
		});
		 
		request.fail(function(jqXHR, textStatus) {
			try{
				throw new Error('Request failed: ' + textStatus );
			}
			catch (ex){
				alert(ex.message); /*** Send this to the server for
				 logging when in production ***/
			}
			finally{
				/*Remove the loading.gif file via jquery and CSS*/
				$("#loadingPic").removeClass("loadGIF");
					
				/*clear the ajax object after use*/
				request = null;
			}
		});
	}
	catch (ex){
		alert(ex.message); /*** Send this to the server for logging when in
				   production ***/
	}
}

Tip: If you don't want to display the empty child-grid, you can make the childDiv invisible in the admin.php view.

<div id="childDiv" style="visibility:hidden" >

Then simply toggle the visibility in the above Ajax function with:

$("#childDiv").css("visibility", "hidden"); or
$("#childDiv").css("visibility", "visible");

That should do the trick!

Choosing between CHtml::ajax and $.ajax ¶

You can either use CHtml::ajax or $.ajax (also called JQuery.ajax) (see http://api.jquery.com/jQuery.ajax/ for more examples).

CHtml::ajax and $.ajax do the same job. However CHtml::ajax is a Yii based PHP function. It must be stored in the view and not in a separate javascript file.

If you want to store your function in a separate javascript file, then use $.ajax.

"Both CHtml::ajax and $.ajax will take care of browser inconsistencies and will also help you with all the "readyState" and "ActiveXObject" (pure ajax) stuff. You don't have to worry about such things anymore, just focus on the interesting parts." (thank you for clearing that up Haensel).

Personally, I prefer putting my functions in separate javascript files, because it allows you to re-use your code. So if you give all your parentDiv/parent-grids the same ID and all your childDiv/child-grids another same ID, then the ajax function should work for all your parent-child views. If you don't want to give them the same ID, but still only want a single ajax function, then you will have to pass the ID to the function.

Haensel also mentioned that $.ajax makes debugging easier. Some experts also say that $.ajax gives you more control.

3. Using a button to do the ajax - Method-3 ¶

As time goes by, new or improved widgets are developed and shared between developers. An example of such is Clevertech's Yii Booster, Yii Bootstrap and Yii Boilerplate family, based on Twitter Bootstrap and HTML5 Boilerplate (both will save you time in future).

Yii Booster has a lovely extension on the CGridView which they call TbExtendedGridView. This gridview has lots of nice features including editable columns, column totals and build in dynamic parent-child gridviews called TbRelationalColumn. If you click on a button in the parent record, a huge new row appears in the gridview, just below the parent record. In this new row, an entire child-gridview appears with all the related records.

However, the technology is still new and I can't get the sorting, filtering and pagination of this nested child-gridview working (most probably because the child-records don't have their own dataprovider and are thus read via relational query). So there is a challenge for all you boffins!!!

So for the moment, I am sticking to my own parent-child gridview methods - discussed in this wiki. But, I am changing all my gridviews to TbExtendedGridView, so that I could use all the other goodies.

But since TbExtendedGridView allows more events to update the parent-grid and its columns, you might now need more control over what events should also update the child-grid. So instead of clicking any place on the parent-row, I now use a special button in the parent-row that updates the child-grid.

The button sends the parentID directly to actionAdmin in our controller, without using our own custom ajax any more. So you can remove the section at the bottom of the parentView, which loaded our own custom ajax function.

$this->widget('zii.widgets.grid.CGridView', array(   
 OR   
$this->widget('bootstrap.widgets.TbExtendedGridView', array(
	'ajaxUpdate' => 'childView', //or 'ajaxUpdate'=>'child-grid' /*keep this line*/
	...
	'afterAjaxUpdate' => "updateChild", /*Remove this line*/
	'selectionChanged'=>"updateChild", /*Remove this line*/
	...
	array(
		'class'=>'CButtonColumn',
		'template'=>'{view} {update} {children}', /*Important: Add the children
			button to the template.*/
		'buttons'=>array(
			'view'=>array(
				...
			),
			'update'=>array(
				...
			),
			'children' => array(
				'label'=>'View Related Records',
				'url'=>'$this->grid->controller->createUrl("admin", array(
					"parentID"=>$data->primaryKey,
				))',
				'options' => array(
					'ajax' => array(
						'type' => 'get',
						'url'=>'js:$(this).attr("href")',
						'success' => 'function(response){
							jQuery("#childDiv").html(response);
							/* you may add additional javascript statements
					 		here - such as making childDiv visible etc. */
						}',
					),
				),
			),
		),
	),

Records and models ¶

I often talk about records instead of models or model instances – but I think you get the idea. For those who do not know it yet (like myself, when I switched to OOP) the differences between records and models are:

a record is a single row of data in a database table;

a model consists of many things such as:

1. the record;

2. rules to be applied to each record;

3. rules for filtering records;

4. custom naming of fields in the record;

5. relations with other models;

6. your own custom functions;

7. arrays of data that you want to use in your code;

8. anything else you want to add – maybe sql, etc.;

Another use case: Child-grid in create and update views ¶

Overview ¶

I put the parent and child gridviews in the 'admin' view, but the following use case of the 'create' and 'update' views, will allow you to add/delete permissions to roles by adding/deleting records directly in the junction table.

In the Admin view, the user clicks on an update button of the role-grid, which displays the update view for that role.

At the top of the update view, you have the role’s data, as normal.

Below that, you have a child gridview, displaying the permissions linked to the above role.

Give the child gridview delete buttons that use the RolePermissionController to delete the records from the junction table. (The child gridview is only displayed when parent records are updated - not when they are created.)

Below the child gridview, add a dropDownList where the user can select new permissions (using child_models or maybe the Permission model directly) to be linked to the role (new records are added to the junction table in the RoleController).

Be careful: Be very careful when deleting records. If your database is using cascading to ensure referential integrity, you might be deleting records from other tables without even knowing it. So rather just flag your records as being deleted (and then scope them out with "default scope" or something) or at least test to make sure the records have not been referenced in other tables.

Although this is not a pure "dynamic gridviews" scenario, it is very handy.

The RoleController ¶

/**
 * Creates a new model.
 * If creation is successful, the browser will be redirected to the 'view' page.
 */
public function actionCreate()
{
	$parent_model=new Role;
	$parentID = 0;

	// Uncomment the following line if AJAX validation is needed
	// $this->performAjaxValidation($parent_model);
	
	/* Create a single child-model instance which will hold the child-grid's
	filtering parameters entered by the user (not the gridview's data records).
	Put the child-model instance, in the searchIncludingPermissions scenario. */
	$child_model = new RolePermission("searchIncludingPermissions");
		
	/* Empty the newly created child-model instance to clear all parameters.*/
	$child_model->unsetAttributes();
		
	/*Test if the event currently using this action passed it any data to save*/
	if(isset($_POST['Role']))
	{
		$parent_model->attributes=$_POST['Role'];
			
		if($parent_model->save())/* Save the Role model */
		{
			/*The new role_id (auto increment) is only available after
			 the parent record was saved. It is needed to create the
			 child records. */
			$parentID = $parent_model->role_id;
				
			/*Test if the dropDownList, which uses a child_model
			 (RolePermission), passed any data in its permission_id
			 array */
			if(($_POST['RolePermission']['permission_id'])<>'')
			{
				foreach ($_POST['RolePermission']['permission_id']
				as $permissionId) {
					$this->linkChildRecord($parentID, $permissionId);
				}
			}
				
			/*Redirect to actionUpdate, because if you stay on the
			 create view a duplicate record would be created if the 
			user clicks the "Save" button */
			$this->redirect(array('update','id'=>$parentID));
		}
	}

	/*Render the create view - passing it all the filtering data it might need*/
	$this->render('create',array(
		'parent_model'=>$parent_model,
		'child_model'=>$child_model,
		'parentID' => $parentID
	));
}

/**
 * Updates a particular model.
 * If update is successful, the browser will be redirected to the 'view' page.
 * @param integer $id the ID of the model to be updated
 */
public function actionUpdate($id)
{
	$parent_model=$this->loadModel($id);
	$parentID = $id;
		
	// Uncomment the following line if AJAX validation is needed
	// $this->performAjaxValidation($parent_model);

	/*Test if the event currently using this action passed it any data to save*/
	if(isset($_POST['Role']))
	{
		$parent_model->attributes=$_POST['Role'];
		if($parent_model->save())/* Save the Role model */
		{
			/*Test if the dropDownList, which uses a child_model
			 (RolePermission), passed any data in its permission_id
			 array */
			if(($_POST['RolePermission']['permission_id'])<>'')
			{
				foreach ($_POST['RolePermission']['permission_id']
				as $permissionId) {
					$this->linkChildRecord($parentID, $permissionId);
				}
			}
			
			/* Here I choose to stay on the update view and not to
			 redirect*/
			/*$this->redirect(array('view','id'=>$parent_model->
			role_id));*/
		}
	}

	/* Create a single child filtering-model instance  */
	$child_model = new RolePermission("searchIncludingPermissions");
		
	/* Empty the newly created child-model instance to clear all parameters.*/
	$child_model->unsetAttributes();
		
	/* Test if the event that is currently calling this action, passed any
	filtering parameters that the user might have entered in the child-grid.
	If true, store these parameters in the newly created child-model instance.*/
	if(isset($_GET['RolePermission']))
		$child_model->attributes=$_GET['RolePermission'];
		
	/*Render the update view - passing it all the filtering data it might need*/
	$this->render('update',array(
		'parent_model'=>$parent_model,
		'child_model'=>$child_model,
		'parentID' => $parentID
	));
}

/*This function is used by both the create and update actions, to create the 
records in the junction table */
private function linkChildRecord($parentID, $permissionId)
{
try { 
	/*Test if a RolePermission record with this "role_id ($parentID) &
	 permission_id"	combination already exists*/
		
	/* I used injection safe DAO sql, because it is faster than
	ActiveRecord and here we don't need all the model functionality that 
	ActiveRecord provides */
	$sql=
	"SELECT	cap_role_permission.rolepermission_id
	 FROM cap_role_permission
	 WHERE
		cap_role_permission.role_id=:varRoleId and
		cap_role_permission.permission_id=:varPermissionId";
			 
	$connection=Yii::app()->db;
	$command=$connection->createCommand($sql);
	$command->bindValue(':varRoleId',$parentID);
	$command->bindValue(':varPermissionId',$permissionId);
	$row=$command->queryRow();
	If ($row <> ""){
		/* Record already exists in RolePermission. Take no action or let
		 the user know. */
	}
	else{ /* Insert the new RolePermission record. */
		try{ 
			$rolePermission = new RolePermission;
			$rolePermission->role_id = $parentID;
			$rolePermission->permission_id = $permissionId;
			$rolePermission->save();
		}
		catch(Exception $e){
			echo($e);
		}
	}
			
}
catch(Exception $e) 
{
	echo($e);/* an exception is raised if ANY of the sql statements fails */
}
}

/*If you have lots of validation rules for your junction table (role_permission), then it is better to use ActiveRecord. The above function could look like this: */
private function linkChildRecord($parentID, $permissionId)
{
	$model=new RolePermission;
	$model->role_id =  $parentID;
	$model->permission_id =  $permissionId;
	$model->save();
}

The views ¶

views/role/create.php

<h1>Create Role</h1>

<?php
	echo $this->renderPartial('_form', array(
	'parent_model'=>$parent_model,
	'child_model' => $child_model,
	'parentID' => $parentID,
	));
?>

views/role/update.php

<h1>Update Role <?php echo $parent_model->role_id; ?></h1>

<?php
	echo $this->renderPartial('_form', array(
	'parent_model'=>$parent_model,
	'child_model' => $child_model,
	'parentID' => $parentID,
	));
?>

views/role/_form.php is used by both create.php and update.php.

<div class="form">
	
	<?php $form=$this->beginWidget('CActiveForm', array(
			'id'=>'role-form',
			'enableAjaxValidation'=>false,
		)); ?>
	
		<div class="solid_border">
			<p class="subsectionheading1">
				<?php
					If(!$parent_model->isNewRecord){					
						echo ("Data fields for Role " . $parentID );
					}
					else{
						echo ("Data fields for new Role");
					}
				?>
			</p>
			
			</br>
			
			<p class="note">Fields with <span class="required">*</span>
			are required.</p>

			<?php echo $form->errorSummary($parent_model); ?>

			<div class="row">
				<?php echo $form->labelEx($parent_model,'role_desc'); ?>
				<?php echo $form->textField($parent_model,'role_desc',array
				('size'=>60,'maxlength'=>64)); ?>
				<?php echo $form->error($parent_model,'role_desc'); ?>
			</div>

		</div></br>
		
		<!-- Use PHP if-statement that allows HTML in result -->
		<?php if (!$parent_model->isNewRecord) : ?>
			<div id="childgrid" class="solid_border">
				<p class="subsectionheading1">Role-Permissions currently linked
				to Role <?php echo $parentID ?></p>
				<?php
					$this->widget('zii.widgets.grid.CGridView', array(
						'id'=>'child-grid',
						'dataProvider'=>$child_model->searchIncludingPermissions
						($parentID),
						'filter'=>$child_model,
						'columns'=>array(
							'permission_id',
							array(
								'name'=>'permission_desc_param',
								'value'=>'($data->relPermission)?$data->
								relPermission->permission_desc:""', 
								'header'=>'Permission Description',
								'filter' => CHtml::activeTextField($child_model,
								'permission_desc_param'),
							),
							array(
								'class'=>'CButtonColumn',
								'template'=>'{delete}',
								'deleteButtonUrl' => 'array
								("rolepermission/delete", "id"=>$data->
								rolepermission_id)',
								'deleteButtonLabel' => 'Delete Link',
								'deleteButtonImageUrl' => Yii::app()->request->
								baseUrl.'/images/css/gridview/delink.png',
								'deleteConfirmation' => 
								"Are you sure you want to detach this Permission
								from the Role?\n\n (Neither the Permission nor
								the Role will be deleted. Only the link between
								them (RolePermission) will be deleted.)", 
							),
						),
					));
				?>
			</div></br>
		<?php endif; ?>
			
		<div class="solid_border">
			<p class="subsectionheading1">
				<?php
					If(!$parent_model->isNewRecord){
						echo ("Permissions that can be linked to Role " .
							 $parentID );
					}
					else{
						echo ("Permissions that can be linked to the new Role ");
					}
				?>
			</p>
			<div class="textaligncenter">
				</br>
				<?php
					$listData = CHtml::listData(Permission::model()->findAll(),
							'permission_id', 'permission_desc'); 
					
					asort($listData); /* sort dropDownList data */
		 
					echo $form->dropDownList($child_model,'permission_id',
						$listData,
						array(
							'id'=>'newPermissions',
							'multiple' => 'multiple',
							'size'=>'6')				
						);
				?>
							
				<?php echo $form->error($child_model,'permission_id'); ?>
			</div>
		</div>

		</br>
		
		<!-- Display the submit button on the BottomBar -->
		<div id="shortBottomBar"> 
			<?php echo CHtml::submitButton($parent_model->isNewRecord ?
				 'Create' : 'Save'); ?>
		</div>
		
	<!-- The dropDownList must be included BEFORE this endWidget() function,
	 otherwise its selected rows will not be submitted to the controller -->
	<?php $this->endWidget(); ?>
	
</div><!-- form -->

Fix the submit button to the bottom of the screen ¶

If you also want to fix your submit button to the bar at the bottom of the screen you need to add a longBottomBar, which is displayed permanently. The button is displayed with a shortBottomBar, which is rendered on top of the longBottomBar.

I like this feature a lot, because the button is always visible. So the user don't need to scroll down in order to submit a long form.

css/main.css:

div#longBottomBar
 {
	position:fixed;
	bottom:0;
	display: inline;  /* display direction inline */
	padding: 3px;
	width: 100%;
	background-color: #141414;
	height:28px;
	text-align: center;
	z-index: 10;       /* Z-index = 10. Move to back. */
 }
 @media screen
 {
body>div#longBottomBar{position: fixed;}
 }

div#shortBottomBar 
 {
	position:fixed;
	bottom:0;
	display: inline;
	padding: 3px;
	width: 565px;
	background-color: #141414;
	height:28px;
	text-align: center;
	z-index: 15;   /* Z-index = 15. Move in front of longBottomBar. */
 }
 @media screen
 {
body>div#shortBottomBar{position: fixed;}
 }

in views/layouts/main.php:

<head>
	...	
</head>

<body>
	...
	
	<div id="longBottomBar">	
	</div>
</body>

Any suggestions for corrections and further improvements are welcome.

Thank you for your inputs softark and Haensel.

Gerhard