- array_map: documentation ( source)
- print_r: documentation ( source)
- array_replace: documentation ( source)
<?php
$arr1= array('a' => "XL");
$arr2= array('a' => "XLd",'b'=>"CDW");
$arr2 = array_replace(array_map(create_function('$n', 'return "";'), $arr2), $arr1);
print_r($arr2);