3v4l.org

run code in 300+ PHP versions simultaneously
<?php $str = "####KELLY##### and ###ANOTHER###### not ####foo#### but: ###SHARE###MIDDLE###HASHES### ?"; echo $str . "\n"; echo preg_replace_callback( '/#{3}\K[A-Z]+(?=#{3})/', function($m) { return str_repeat('#', strlen($m[0])); }, $str );

preferences:
26.78 ms | 405 KiB | 5 Q