Set a multidimensional array element based on an array of nested keys.

array_set_nested_element

/**
 * Set a multidimensional array element based on an array of nested keys.
 *
 * @code
 *   $vars   = array();
 *   $string = 'some.string.of.keys';
 *   $keys   = explode('.', $string);
 *   $value  = 'final value';
 *   array_set_nested_element($vars, $keys, $value);
 * @endcode
 *
 * The end result is $vars['some']['string']['of']['keys'] = 'final value';
 *
 * @param  array &$array The base array.
 * @param  array &$keys An array of keys, each successive a child of the former.
 * @param  mixed $value The final value to set on the last child key.
 *
 * @author  Aaron Klump <sourcecode@intheloftstudios.com>
 */
function array_set_nested_element(&$array, &$keys, $value) {
  if (!($key = array_shift($keys))) {
    $array = $value;
    return;
  }
  if (!isset($array[$key])) {
    $array[$key] = array();
  }
  $self = __FUNCTION__;
  return $self($array[$key], $keys, $value);
}