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<?php $a = array('a'=>1,'b'=>2,'c'=>3); var_dump(array_reduce($a, function($result, $item) use ($a) { //$key = $result ? key($result) : $a; //$key = $key == 'a' ? 'aa' : $key; $result[] = $item; return $result; }));

preferences:
49.53 ms | 402 KiB | 5 Q