Migrating from PHP 5.4.x to PHP 5.5.x

• What has changed in PHP 5.5.x
• Backward Incompatible Changes
• New features
• Deprecated features in PHP 5.5.x
• Changed Functions
• New Functions
• New Classes and Interfaces
• New Methods
• Other changes to extensions
• New Global Constants
• Changes to INI file handling
• Changes to PHP Internals

See also the migration guides for PHP versions 5.0.x, 5.1.x, 5.2.x, 5.3.x and 5.4.x.