note 28892 modified in function.array-unique by vrana

To get a list of the duplicated values in an array, array_unique isn't much help. Instead, use array_filter in conjunction with a callback function, as below: <?php $checkKeysUniqueComparison = create_function('$value','if ($value > 1) return true;'); $result = array_keys (array_filter (array_count_values($array), $checkKeysUniqueComparison)); ?> These two lines therefore will create $result, an array of duplicated values in the array $array, once each. E.g. the array $array = array ("a", "b", "a", "b", "x", "y", "z", "x"); gives the result Array([0] => a [1] => b [2] => x) --was-- To get a list of the duplicated values in an array, array_unique isn't much help. Instead, use array_filter in conjunction with a callback function, as below: $checkKeysUniqueComparison = create_function('$value','if ($value > 1) return true;'); $result = array_keys (array_filter (array_count_values($array), $checkKeysUniqueComparison)); These two lines therefore will create $result, an array of duplicated values in the array $array, once each. E.g. the array $array = array ("a", "b", "a", "b", "x", "y", "z", "x"); gives the result Array([0] => a [1] => b [2] => x) http://php.net/manual/en/function.array-unique.php