Changed Functions

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.

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.