Is there an alternative to mysql_real_escape_string for PHP. I want to remove any javascript or php code entered into the text box.
That's not what mysql_real_escape_string does or did (the functions are now deprecated). An alternative to mysql_real_escape_string is using prepared statements, for example with PDO or MySQLi.
However, that's completely unrelated to stripping Javascript or PHP code from a string - also; it could be relatively hard to identify 'Javascript' or 'PHP'.
The real question here is; why do you wanna strip it? The danger doesn't reside in saving the data, the danger resides in displaying the data. You should never ever execute code entered by the user, be it Javascript or PHP.
As for Javascript, disallowing HTML tags in your output is enough. Look into functions as strip_tags, or even better, htmlspecialchars. Preventing PHP from execution is even easier; just do not use the method eval.