3v4l.org

run code in 200+ php & hhvm versions
Bugs & Features
<?php $filter = 'ololo'; $k = "substr('filter',1,1)"; echo ${$k};
Output for 5.0.4 - 7.2.0
Notice: Undefined variable: substr('filter',1,1) in /in/smBFr on line 4
Output for 4.3.0 - 5.0.3
Notice: Undefined variable: substr('filter',1,1) in /in/smBFr on line 4