3v4l.org

run code in 150+ php & hhvm versions
Bugs & Features
<?php $string = '919191911'; $pattern = '(\\d)(?=(\\d{3})+$)'; $replacement = '$1$4 $2$3$5'; echo preg_replace($pattern, $replacement, $string);
Output for 4.3.11 - 5.6.28, 7.0.0 - 7.1.0
Warning: preg_replace(): Unknown modifier '(' in /in/YERS8 on line 5
Output for hhvm-3.10.0 - 3.12.0
Warning: Unknown modifier '(': [(\d)(?=(\d{3})+$)] in /in/YERS8 on line 5
Output for 4.3.0 - 4.3.10
Warning: Unknown modifier '(' in /in/YERS8 on line 5