3v4l.org

run code in 200+ php & hhvm versions
Bugs & Features
<?php $a = "abab"; preg_replace("/(a)/", "$1-", $a); echo $a;
based on oXmCI
Output for 5.6.0 - 5.6.30, hhvm-3.15.4, 7.0.0 - 7.3.1
abab