Drupal Array Merge - copied from swftools_array_merge().

drupal_array_merge.php

<?php
/**
 * Merges two multi-dimensional arrays.
 * 
 * Taken from http://drupalcontrib.org/api/search/6/swftools_array_merge
 * 
 * This function is used by players that filter their settings to strip out
 * blanks or defaults. For the admin page we need a full set of values to prevent
 * errors. Since the arrays might be multi-dimensional we cannot use a regular
 * array_merge(). The values in the first array will be over-written by values in
 * the second, if they exist.
 * 
 * @param array $array1
 *   The first array to merge.
 * @param array $array2
 *   The second array to merge.
 *   
 * @return array
 *   The result of the merge.
 */
function drupal_array_merge($array1, $array2) {

  // Iterate over $array 2 (this is normally the smaller of the two)
  foreach ($array2 as $key => $value) {

    // If this key is present in $array1 then work out what to do
    if (isset($array1[$key])) {

      // If both keys hold arrays, combine them    
      if (is_array($value) && is_array($array1[$key])) {
        $array1[$key] = drupal_array_merge($array1[$key], $value);
      }
      else {
        // Replace value in $array1 with that from $array2
        $array1[$key] = $value;
      }
    }
    else {
      // Simply put this value in $array1 if it isn't already in $array1
      $array1[$key] = $value;
    }

  }
  
  // Return the result
  return $array1;

}