regex - Validate date format in php

Question

I'm trying to validate date using PHP.

I'd like following formats to be valid:

d/m/yy
d/m/yyyy
dd/m/yy
dd/m/yyyy
d/mm/yy
d/mm/yyyy
dd/mm/yy
dd/mm/yyyy

I've tried many regular expressions and different variations of checkdate() function. Currently I have something like this:

function _date_is_valid($str)
{
     if(strlen($str) == 0)
         return TRUE;
     if(substr_count($str,'/') == 2)
     {
         if (preg_match("/^((((31/(0?[13578]|1[02]))|((29|30)/(0?[1,3-9]|1[0-2])))/(1[6-9]|[2-9]d)?d{2})|(29/0?2/(((1[6-9]|[2-9]d)?(0[48]|[2468][048]|[13579][26])|((16|[2468][048]|[3579][26])00))))|(0?[1-9]|1d|2[0-8])/((0?[1-9])|(1[0-2]))/((1[6-9]|[2-9]d)?d{2}))/", $str))
         {
             $datearray = explode('/',$str);
             if($datearray[2] > 2030)
                 return FALSE;
             return checkdate($datearray[1], $datearray[0], $datearray[2]);
         } 
         else 
         {
             return FALSE;
         }
     }
     return FALSE;
}

This however, validates dates like 11/11/200 and 11/11/200#

How can I validate date to match required format?

Edit: I could check datearray[2] to be between 10 and 30 and 2010 and 2030. But is there a way to check it using regex?

Edit1: return TRUE on strlen($str) == 0 is because I want users to be able to add events without knowing when will the event occur so someone else can qualify the schedule and assign event to certain date later

---

Just for the record. I ended up doing:

function _date_is_valid($str)
{
    if(strlen($str) == 0) //To accept entries without a date
        return TRUE;
    if(substr_count($str,'/') == 2)
    {
        list($d,$m,$y) = explode('/',$str);
        if(($y >= 10 && $y <= 30) || ($y >= 2010 && $y <= 2030))
        {
            return checkdate($m,$d,$y);
        }
    }
    return FALSE;
}

Thanks for all your answers

Answer 1

function _date_is_valid($str) {
    if (substr_count($str, '/') == 2) {
        list($d, $m, $y) = explode('/', $str);
        return checkdate($m, $d, sprintf('%04u', $y));
    }

    return false;
}