New features
Changed Functions
Migrating from PHP 5.4.x to PHP 5.5.x
PHP Manual

## Deprecated features in PHP 5.5.x

### ext/mysql deprecation

The original MySQL extension is now deprecated, and will generate `E_DEPRECATED` errors when connecting to a database. Instead, use the MySQLi or PDO_MySQL extensions.

### preg_replace /e modifier

The preg_replace /e modifier is now deprecated. Instead, use the preg_replace_callback function.

### intl deprecations

IntlDateFormatter::setTimeZoneID and datefmt_set_timezone_id are now deprecated. Instead, use the IntlDateFormatter::setTimeZone method and datefmt_set_timezone function, respectively.

### mcrypt deprecations

The following functions have been deprecated:

- mcrypt_cbc
- mcrypt_cfb
- mcrypt_ecb
- mcrypt_ofb