3v4l.org

run code in 300+ PHP versions simultaneously
<?php $a = array(1,2,3,4); $b = array('a', 'b', 'c'); print_r($a); array_walk($a, function(&$item) use ($a) { $item *= 2; }); print_r($a);

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36.65 ms | 402 KiB | 5 Q