3v4l.org

run code in 200+ php & hhvm versions
Bugs & Features
<?php $string = 'abc'; var_dump(preg_replace_callback( '/(.)/', function ($m) { static $counter = 1; return 'foo' . $counter++; }, $string ));
based on ZgbUT
Output for 5.6.0 - 5.6.30, hhvm-3.18.5 - 3.22.0, 7.1.0 - 7.3.0beta1
string(12) "foo1foo2foo3"