can't run PATH_SEPARATOR constant

[narjis]

I am using php version 5.3.0 and when i use the following statement i get error undefined fconsta=nt PATH_SEPERATOR. Please sommebody guide how to remove this error.

Here is the code

<?php

define ("APP_PATH",realpath("."));
//include_once("com/user.php");
$path = array("APP_PATH",
		  "APP_PATH" . '/com',
		  get_include_path()
		  );
		 set_include_path(implode(PATH_SEPARATOR,$path));

function __autoload($classname){
require_once $classname.".php";
}
$user = new user;

echo ($user->get_name());
?>