Nginx secure link test

Nginx securelink
location /on_play {
				alias /webmedia;
				secure_link $arg_st,$arg_e;
        secure_link_md5 mysecret$uri$arg_e;



        if ($secure_link = "")
            return 403;
        }

        if ($secure_link = "0") {
            return 403;
        }


        }


<?php

$secret = 'mysecret';
 $path = '/on_play/vid3.mp4';

 $expire = time()+300;

 $md5 = base64_encode(md5($secret . $path . $expire, true));
 $md5 = strtr($md5, '+/', '-_');
 $md5 = str_replace('=', '', $md5);


 echo '<br>http://sample.com/on_play/vid3.mp4?st='.$md5.'&e='.$expire;
 ?>