The PHP development team released version 7.3.0 that comes with numerous improvements and new features such as

• Flexible Heredoc and Nowdoc Syntax
• PCRE2 Migration
• Multiple MBString Improvements
• LDAP Controls Support
• Improved FPM Logging
• Windows File Deletion Improvements
• Several Deprecations

The list of changes is recorded in the ChangeLog. The migration guide is available in the PHP Manual.

Both Yii 2.0 and upcoming Yii 3.0 releases will be comatible with new PHP release.