PHP array_diff

array_diff() function compares arrays and returns all the elements in the 1st array but not in the 2nd array.
   array array_diff(array array 1, array array 2 [, array ...])

<?PHP
	$arr1=array(1,2,3,4,5,6,7,8,9);
	$arr2=array(2,4,6,8);
	$arr3=array_diff($arr1,$arr2);
	foreach($arr3 as $element) echo "$element, "; //1, 3, 5, 7, 9,
?>

It can also take a 3rd array parameter. It returns all the elements in the 1st array but not in the 2nd and 3rd array.

<?PHP
	$arr1=array(1,2,3,4,5,6,7,8,9);
	$arr2=array(2,4,6,8);
	$arr3=array(1,3);
	$arr=array_diff($arr1,$arr2,arr3);
	foreach($arr as $element) echo "$element, "; //5, 7, 9, 
?>

Similarly, more arrays can be taken, all elements in the 1st array as well as in the other arrays will be deleted.

<?PHP
	$arr1=array(1,2,3,4,5,6,7,8,9);
	$arr2=array(2,4,6,8);
	$arr=array_diff($arr1,$arr2,array(1,3),array(5));
	foreach($arr as $element) echo "$element, "; //7, 9, 
?>

It can also take associative arrays, both the keys and values will be compared.

<?PHP
	$arr1=array("apple"=>2.2,"rice"=>0.5,"nuts"=>4.99,"meat"=>6.99);
	$arr2=array("apple"=>1.2,"rice"=>0.5,"orange"=>1.99);
	$arr = array_diff($arr1,$arr2);
	print_r($arr);

    //the result is:
	Array
	(
		[apple] => 2.2
		[nuts] => 4.99
		[meat] => 6.99
	)
?>

array_diff_key() function compares only array keys and returns all the elements in the 1st array but not in the following arrays.

<?PHP
	$arr1=array("apple"=>2.2,"rice"=>0.5,"nuts"=>4.99,"meat"=>6.99);
	$arr2=array("apple"=>1.2,"rice"=>0.5,"orange"=>1.99);
	$arr = array_diff_key($arr1,$arr2);
	print_r($arr);

    //the result is:
	Array
	(
		[nuts] => 4.99
		[meat] => 6.99
	)
?>

array_intersect() function returns the shared elements of the 1st array and other arrays.

<?PHP
	$arr1=array(1,2,3,4,5,6,7,8,9);
	$arr2=array(2,4,6,8);
	$arr3=array_intersect($arr1,$arr2);
	foreach($arr3 as $element) echo "$element, "; //2, 4, 6, 8,
?>