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<?php $arr = [ [[58 => 32]], [[58 => 34]], [[57 => 26]], [[57 => 27]], [[56 => 16]], [[56 => 17]] ]; array_walk_recursive($arr, function($v,$k) use (&$r){ $r[$k] = isset($r[$k]) ? ($r[$k]+$v) : $v; }); print_r($r);

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57.34 ms | 402 KiB | 5 Q