3v4l.org

run code in 150+ php & hhvm versions
Bugs & Features
<?php print preg_replace('/(?<=[a-zA-Z0-9])([A-Z0-9])(?=[a-zA-Z0-9])/', "_$1", 'spbAddress1');
based on Hqr67
Output for 4.3.0 - 5.2.3, 5.2.5 - 7.1.0
spb_Address1
Output for 5.2.4

Process exited with code 137.