<?php $A = [3,45,67,8]; $B = [ 1 => [1,6,8], 2 => [5,67,3,4,5,66,6], 3 => [55,56,57,58], 4 => [45,80,81,82] ]; $result = []; foreach ($B as $key => $haystack) { foreach ($haystack as $hay) { if (in_array($hay, $A)) { $result[] = $key; break; } } } var_export($result);
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