3v4l.org

run code in 300+ PHP versions simultaneously
<?php echo preg_replace_callback('/([a-z])(_[a-z])/', function($u) { var_dump($u); return ucwords(str_replace('_', '', $u[1])); } , 'rob_tr_yuui'); echo PHP_EOL; echo preg_replace('/([a-z])(_[a-z])/', '$1.$2', 'rob_tr_yuui');

preferences:
38.92 ms | 402 KiB | 5 Q