array_intersect
    (PHP 4 >= 4.0.1, PHP 5)
array_intersect -- Computes the intersection of arrays
Description
array 
array_intersect ( array array1, array array2 [, array ...] )
     array_intersect() returns an array
     containing all the values of array1
     that are present in all the arguments.
     Note that keys are preserved.
    
     
Example 1. array_intersect() example 
<?php $array1 = array("a" => "green", "red", "blue"); $array2 = array("b" => "green", "yellow", "red"); $result = array_intersect($array1, $array2); ?>
 |  
 
       This makes $result have
       
Array (     [a] => green     [0] => red )
 |  
  | 
    Note: 
      Two elements are considered equal if and only if
      (string) $elem1 === (string) $elem2. In words:
      when the string representation is the same.
      
     
     See also array_intersect_assoc(),
     array_diff(), and
     array_diff_assoc().