3v4l.org

run code in 300+ PHP versions simultaneously
<?php $trim = function($str) { return preg_replace("~(?|\({2,}" . ($p = "(\(((?:[^()]*|(?1))*)\))") . "\){2,}|^(((\([^()]+\))+))$|$p)~", '$2', $str); }; echo $trim('((((A))))'), "\n"; echo $trim('(((((B+C)*A)*(F))))'), "\n"; echo $trim('(A+B)(B+C)'), "\n"; echo $trim('(((((B+C)*A))))'), "\n"; echo str_repeat('-',15), PHP_EOL; echo $trim('((A+B)+C)'), "\n"; echo $trim('(((A+B))+C)'), "\n"; echo $trim('((((A+B)+C))'), "\n"; echo $trim('(A+(B+C))'), "\n"; echo $trim('(A+((B+C)))'), "\n";
Output for 5.6.38, 7.0.0 - 7.0.33, 7.1.0 - 7.1.25, 7.2.0 - 7.2.33, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.28, 8.2.0 - 8.2.19, 8.3.0 - 8.3.7
A ((B+C)*A)*(F) (A+B)(B+C) (B+C)*A --------------- (A+B)+C ((A+B))+C (((A+B)+C) A+(B+C) A+((B+C))
preferences:
124.54 ms | 404 KiB | 218 Q