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run code in 200+ php & hhvm versions
Bugs & Features
<?php $var = array( 'a' => 'a', 'b' => 'b', ); array_walk($var, function($value) { }); var_dump(key($var));
based on LAhFv
Output for 7.1.0 - 7.2.0
string(1) "a"
Output for 5.3.21 - 7.0.20
NULL