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<?php $input = Array ( 'arr1' => Array ( 'JAN2016', 'MAI2013', 'JUN2014', ), 'arr2' => Array ( 'APR2016', 'DEC2013', 'JUN2014', ), 'arr3' => Array ( 'JAN2016', 'MAI2020', 'JUN2022', ) ); $newArray = []; foreach($input as $k=>$values) { foreach($values as $value) { $newArray[$value][] = $k; } } print_r(array_filter($newArray, function($v) { return 1 < count($v); }));
Output for 7.4.0 - 7.4.33, 8.0.1 - 8.0.30, 8.1.0 - 8.1.34, 8.2.0 - 8.2.30, 8.3.0 - 8.3.30, 8.4.1 - 8.4.18, 8.5.0 - 8.5.3
Array ( [JAN2016] => Array ( [0] => arr1 [1] => arr3 ) [JUN2014] => Array ( [0] => arr1 [1] => arr2 ) )

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