(PHP 5)
array_walk_recursive — Apply a user function recursively to every member of an array
   Applies the user-defined function funcname to each
   element of the input array. This function will recurse
   into deeper arrays.
  
inputThe input array.
funcname
       Typically, funcname takes on two parameters.
       The input parameter's value being the first, and
       the key/index second.
      
Note:
If
funcnameneeds to be working with the actual values of the array, specify the first parameter offuncnameas a reference. Then, any changes made to those elements will be made in the original array itself.
userdata
       If the optional userdata parameter is supplied,
       it will be passed as the third parameter to the callback
       funcname.
      
   Returns TRUE on success or FALSE on failure.
  
Example #1 array_walk_recursive() example
<?php
$sweet = array('a' => 'apple', 'b' => 'banana');
$fruits = array('sweet' => $sweet, 'sour' => 'lemon');
function test_print($item, $key)
{
    echo "$key holds $item\n";
}
array_walk_recursive($fruits, 'test_print');
?>
The above example will output:
a holds apple b holds banana sour holds lemon
You may notice that the key 'sweet' is never displayed. Any key that holds an array will not be passed to the function.