mysql_real_escape_string or strip_tags - Which is more Secure

Hi All ,

I am using the below function named it as "protect" and passing every POST variable through it before using it in my PHP script.

function protect($string){ $string = trim(strip_tags(addslashes($string))); return $string;
And then using it as below --

$Customer_id = protect($_POST['cust_id']);

My question is which is more secure , the below mysql_real_escape_string or the above protect function--

$Customer_id = mysql_real_escape_string($_POST['cust_id']);

In both the cases I am going to use the $Customer_id in the MySql query, so just worried about which one us more secure Injection wise.

Thanks