Security Question

In a lot of PHP code that I have seen, there are lines such as this: mysql_connect('localhost', 'mysql_login()', 'mysql_password()'); that is used to "hide" the login and password from someone should they somehow view the code instead of the output of the PHP file. My question is, how do I set up those "functions" mysql_login and mysql_password? Are they just standard functions defined in a header someplace? Or is this even the best, most secure way of handling it? Ryan Shrout