3v4l.org

run code in 500+ PHP versions simultaneously
<?php $a = [ ['a', 'b', 'c'], ['d', 'e', 'f'], ]; array_walk_recursive($a, function(&$v) { $v = strtoupper($v); } ); print_r($a);

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94.18 ms | 1280 KiB | 5 Q