[PHP] Extract unique values of the specified key in a two dimensional array

array_unique_deep.php

<?php
/**
 * Extract unique values of the specified key in a two dimensional array
 *
 * @param array $array
 * @param mixed $key
 * @return array
 */
function array_unique_deep($array, $key)
{
  $values = array();
  foreach ($array as $k1 => $row)
  {
    foreach ($row as $k2 => $v)
    {
      if ($k2 == $key)
      {
        $values[ $k1 ] = $v;
        continue;
      }
    }
  }
  return array_unique($values);
}