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<?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 => $haystack) { if (array_intersect($haystack, $A)) { $result[] = $key; } } var_export($result);
Output for 5.6.38, 7.1.0 - 7.1.23, 7.2.0 - 7.2.33, 7.3.16 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.27, 8.2.0 - 8.2.17, 8.3.0 - 8.3.4
array ( 0 => 1, 1 => 2, 2 => 4, )

preferences:
179.38 ms | 403 KiB | 169 Q