PHP array_intersect()

array_intersect() function returns the shared elements of array1 and other arrays.
   array array_intersect(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);
	$arr3=array_intersect($arr1,$arr2);
	foreach($arr3 as $element) echo "$element, "; //2, 4, 6, 8,
?>

If more than 2 arrays are compared, only elements contained in all arrays will be returned.

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

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);
	$arr = array_intersect($arr1,$arr2);
	print_r($arr);

    //the result is:
	Array
	(
		[rice] => 0.5
	)
?>

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

array_intersect_key() function compares array keys and returns all the elements in the 1st array as well as 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);
	$arr = array_intersect_key($arr1,$arr2);
	print_r($arr);
	
	//the result is:
	Array
	(
		[apple] => 2.2
		[rice] => 0.5
	)	
?>