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<?php $data1 = array("Peter" => "1", "Ann" => "1", "Susan" => "2", "Tom"=> "3"); $find = 1; Var_dump(array_keys(array_intersect($data1, [$find])));
Output for 5.6.0 - 5.6.40, 7.0.0 - 7.0.33, 7.1.0 - 7.1.33, 7.2.0 - 7.2.34, 7.3.0 - 7.3.33, 7.4.0 - 7.4.33, 8.0.0 - 8.0.30, 8.1.0 - 8.1.33, 8.2.0 - 8.2.29, 8.3.0 - 8.3.27, 8.4.1 - 8.4.14
array(2) { [0]=> string(5) "Peter" [1]=> string(3) "Ann" }
preferences:
133.5 ms | 408 KiB | 5 Q