require versus require_once

[klycette]

In a standard web app where users were searching the database, registering, logging on, etc, which of these functions would be the one to use and why?

Also, regarding mysql_connect and mysql_pconnect...I know that the p stands for persistent, but I'm wondering under what circumstances you should use each, in layman's terms. Thanks.

[Mordecai]

Require_once is, in essence, always better, but I never use it. If you know what you're doing, you can probably avoid redundantly including (or requiring) a file.

mysql_pconnect() is best used when someone will be accessing the database frequently in a given period of time (usually quite small). The link stays open even when no one is on the page. The downside is that it requires you to close the connection manually (if one pconnect were called for every user logged in, a logout function would most likely close it).