mysql_real_escape more than once

Question

I was just wondering whether it makes a difference if I mysql_real_escape data more than once?

So if I escaped data in one part of my website, and then again in another part of code. Would this be a problem? Or make a difference?

Answer 1

Yes, it makes a difference:

$string = "I'm Chuck!";
mysql_escape_string($string); // I\'m Chuck!
mysql_escape_string(mysql_escape_string($string)); // "I\\\'m Chuck!