Error in your SQL syntax: HELP!

This gives me an error:

  "You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '@example.com, 1200504533,555' at line 1

Here is my PHP

$result = mysql_query("Insert into users_users(user_name, user_pass, user_email, timestamp, user_ip) values(" . mysql_real_escape_string($username) . ", " . mysql_real_escape_string($userpass) . ", " . mysql_real_escape_string($useremail) . ", " . time() .", " . mysql_real_escape_string('111.111.111.111'), $con) or die('Could not query:' . mysql_error());;

I have attached the table structure.Start Free Trial

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CREATE TABLE `users_users` (
  `userid` int(35) NOT NULL auto_increment,
  `user_name` varchar(50) NOT NULL default '',
  `user_pass` varchar(255) NOT NULL default '',
  `user_level` varchar(50) NOT NULL default '',
  `timestamp` int(10) default NULL,
  `user_email` varchar(50) NOT NULL default '',
  `user_ip` varchar(50) NOT NULL default '',
  PRIMARY KEY  (`userid`)
) TYPE=MyISAM AUTO_INCREMENT=132 CHARACTER SET utf8 COLLATE utf8_unicode_ci;