1. The missing echo
2. The echo too much
3. The true false
4. Rules for numbers
5. Rules for enums
6. Rules for foreign keys
7. Ending ?> tag in non-view
8. Semicolon
9. visible option in CMenu and null values

Please join the party by adding your own favorite Yii programming errors. Be sure to leave at least a hint at the correction.

The missing echo ¶

In the view put:

<h1>Edit item: <?php $model->label; ?></h1>

Now spend your time debugging why you are not seeing the value of $model->label even though you are clearly asking for it.

The echo too much ¶

In the view put:

<h1>Edit item: <?php echo $this->widget('CWidget'); ?></h1>

"Object of class CWidget could not be converted to string." A widget may not have an echo.

The true false ¶

In the config file or wherever you are to provide a boolean value, put: ~~~ 'someOption' => 'false', ~~~ Then read the PHP manual to find out why this does not evaluate to false like you wanted it to.

Rules for numbers ¶

In the model rules() method put:

array('count', 'number', 'integerOnly'=>true),

then try

array('count', 'numeric', 'integerOnly'=>true),

and only then look it up: 'numerical'.

Rules for enums ¶

In the model rules() method put:

array('format', 'range', 'in' => array('html', 'rss2', 'atom', 'json', 'xml')),

then later remind yourself that Yii is not SQL.

Rules for foreign keys ¶

In the model rules() method put:

array('foreingKey', 'exists', 'className' => 'SomeModel', 'attributeName' => 'id'),

Sure we have 'exists' method for CActiveRecord model, but ...

Ending ?> tag in non-view ¶

Extend a base class or edit a config file (needs to be included before the sessions starts) and leave a ?> at the ending with at least one trailing white space character. Make sure output buffering is off. Cry manly tears while trying to figure out why "Cannot modify header information - headers already sent" spams your log files.

Semicolon ¶

$total = 0;
foreach($model->rels as $rel);
{
    $total += $rel->count;
}
echo $total; // wrong result!!

I wasted 12 hours debugging this.

visible option in CMenu and null values ¶

Use a parameter feature.enabled to enable/disable a feature through configuration. And then wonder why you still see the menu item, even if you have no feature.enabled parameter at all.

<?php $this->widget('zii.widgets.CMenu', array(
    'items' => array(
        array(
            'label' => 'A new feature',
            'url' => array('feature/view'),
            'visible' => Yii::app()->params['feature.enabled'],
        ),

Yii::app()->params['feature.enabled'] returns null if the parameter is not defined. But in this case that's different from false because CMenu uses isset($items['visible']) which returns false for null values.