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

## Changed Functions

### PHP Core

- set_error_handler() can now be called with `NULL` as an argument to reset the error handler.
- When called with `NULL`, set_error_handler() and set_exception_handler() now return the previous error or exception handler, respectively.
- json_encode() now accepts `depth` parameter.
- The behaviour of pack() and unpack() with the "a" and "A" format codes has changed. Detailed notes on these changes are available.

### intl

- MessageFormatter::format() and related functions now accept named arguments and mixed numeric and named arguments when PHP is linked to ICU 4.8 or later.
- MessageFormatter::format() and related functions no longer error when an insufficient number of arguments have been provided. Instead, the placeholders will not be substituted.
- MessageFormatter::format() and MessageFormatter::parse() are no longer limited to second precision when dealing with times.
- IntlDateFormatter::__construct() and datefmt_create() now accept IntlTimeZone and DateTimeZone objects for the `timezone` argument, and IntlCalendar objects for the `calendar` argument. Furthermore, if the time zone is omitted and the `calendar` doesn't specify a time zone, PHP's default time zone from date_default_timezone_get() is now used instead of the default ICU time zone.
- IntlDateFormatter::getCalendar() and datefmt_get_calendar() return false if the IntlDateFormatter object was created with an IntlCalendar instance instead of one of the IntlDateFormatter constants.
- IntlDateFormatter::setCalendar() and datefmt_set_calendar() now accept IntlCalendar objects in addition to the IntlDateFormatter constants.
- IntlDateFormatter::format() and datefmt_format() now accept IntlCalendar objects.

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