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 ✔ 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