3v4l.org

run code in 200+ php & hhvm versions
Bugs & Features
<?php $string = '919191911'; $pattern = '(\\d)(?=(\\d{3})+$)'; $replacement = '$1$4 $2$3$5'; echo preg_replace($pattern, $replacement, $string);
Output for 4.3.11 - 7.2.0
Warning: preg_replace(): Unknown modifier '(' in /in/YERS8 on line 5
Output for 4.3.0 - 4.3.10
Warning: Unknown modifier '(' in /in/YERS8 on line 5