3v4l.org

run code in 150+ php & hhvm versions
Bugs & Features
<?php $pattern="\( ( (?>[^()]+) | (?R) )* \)"; $str="(def a (x) (+ 1 x))(print (a 1))"; preg_match_all($pattern,$str,$out); var_dump($out);
Output for 5.2.0 - 7.1.0
Warning: preg_match_all(): Delimiter must not be alphanumeric or backslash in /in/WRPKW on line 9 NULL
Output for 4.3.11 - 5.1.6
Warning: preg_match_all(): Delimiter must not be alphanumeric or backslash in /in/WRPKW on line 9 array(0) { }
Output for 4.3.0 - 4.3.10
Warning: Delimiter must not be alphanumeric or backslash in /in/WRPKW on line 9 array(0) { }