3v4l.org

run code in 150+ php & hhvm versions
Bugs & Features
<?php $a = 1; $$a = 1; ${++$a} = ${$a++}; var_dump(${1}); var_dump($a); var_dump(${2});
Output for 5.0.4 - 5.6.28, 7.0.3 - 7.1.0
Notice: Undefined variable: 2 in /in/ISu2l on line 4 int(1) int(3) NULL
Output for 7.0.0 - 7.0.2
int(1) int(3) NULL
Output for 4.3.0 - 5.0.3
Notice: Undefined variable: 2 in /in/ISu2l on line 4 int(1) int(3) NULL