3v4l.org

run code in 150+ php & hhvm versions
Bugs & Features
<?php echo preg_replace("/(?!^)(?[A-Z])/", "_", "FooBarAoo");
Output for 4.4.9, 5.2.6 - 7.1.0
Warning: preg_replace(): Compilation failed: unrecognized character after (? or (?- at offset 7 in /in/NvN3s on line 3
Output for 4.3.11 - 4.4.8, 5.0.0 - 5.2.5
Warning: preg_replace(): Compilation failed: unrecognized character after (? at offset 7 in /in/NvN3s on line 3
Output for 4.3.0 - 4.3.10
Warning: Compilation failed: unrecognized character after (? at offset 7 in /in/NvN3s on line 3