PHP custom function: recursively convert multi-dimensional array to one-dimensional array

function array_multi2single($array)
{
    static $result_array=array();
    foreach($array as $value)
    {
        if(is_array($value))
        {
            array_multi2single($value);
        }
        else
            $result_array[]=$value;
    }
    return $result_array;
}
//测试
$array=array("1"=>array("A","B","C",array("D","E")),"2"=>array("F","G","H","I"));
$array=array_multi2single($array);
echo "测试结果:";
foreach($array as $value)
{
    echo "$value";
    echo "";
}
?>