array_diff Computes the difference of arrays &reftitle.description; arrayarray_diff arrayarray arrayarrays Compares array against one or more other arrays and returns the values in array that are not present in any of the other arrays. &reftitle.parameters; array The array to compare from arrays Arrays to compare against &reftitle.returnvalues; Returns an array containing all the entries from array that are not present in any of the other arrays. Keys in the array array are preserved. &reftitle.examples; "green", "red", "blue", "red"); $array2 = array("b" => "green", "yellow", "red"); $result = array_diff($array1, $array2); print_r($result); ?> ]]> Multiple occurrences in $array1 are all treated the same way. This will output : blue ) ]]> Two elements are considered equal if and only if (string) $elem1 === (string) $elem2. That is, when the string representation is the same. v = $v; } public function __toString() { return $this->v; } } $source = [new S('a'), new S('b'), new S('c')]; $filter = [new S('b'), new S('c'), new S('d')]; $result = array_diff($source, $filter); // $result now contains one instance of S('a'); ?> ]]> To use an alternate comparison function, see array_udiff. &reftitle.notes; This function only checks one dimension of a n-dimensional array. Of course you can check deeper dimensions by using array_diff($array1[0], $array2[0]);. &reftitle.seealso; array_diff_assoc array_udiff array_intersect array_intersect_assoc