PHP 7.1 void return type Nullable types $b) return $a; else return null; } ]]> Iterable pseudo-type Negative string offsets string(1) "e" ]]> List keys Warn about invalid strings in arithmetic Class constant visibility Safe Interrupts The VM now checks for interrupts on each loop iteration, user function entry and internal function exit. This will reduce the number of segfaults and deadlocks when a time out happens. Things that may break your code new 'void' and 'iterable' keywords rand() and srand() are now aliased to mt_rand() and mt_srand() Mersenne Twister algorithm has been tweaked Calling a function with too few args is now an Error instead of a Warning Dropped support for sslv2 streams Dropped support for mcrypt