There's a connection already waiting for you. Yay, right? Well, with MySQL, connecting is actually really really cheap, and frankly, if you are using persistent connections, you might encounter some issues with Apache going zombie on processes that use a connection, effectively taking that connection out of use. Grrr.

She did some research on the topic but found contradicting evidence for both sides. Eventually, what her choice boiled down to was this possible issue mentioned by Jay Pipes (of MySQL):

If you use Apache, Apache can zombie a PHP process and cause the mysql connection to be held until the mysql server restarts...

In this article we take a look the connection methods used for PHP and Oracle database using the PHP OCI8 extension. Specifically we cover non-persistent and persistent connections while offering some suggestions for choosing the right approach. In addition we will cover some upcoming features in the next major release of the Oracle database to significantly improve scalability of PHP applications.

He talks about [pdf] the types of Oracle->PHP connections, what the database name connection strings are (with examples) the environment variables for connections, closing the connections, a look at connection pooling, and an overview of using DRCP (Database Resident Connection Pooling) to accomplish it.

A major drawback is that while browsing from one page to another, the website does not remember the State of the browsing session. This make interactivity almost impossible. In order to increase interactivity, the developer can use the session handling features of PHP to augment the features of HTTP in order to remember the State of the browsing session.

They look at two solutions - using cookies and using sessions. Cookies are simple enough, but when it comes to sessions, there's actually two different roads to follow: with cookies enabled and without. They have to be handled slightly differently, but both essentially work the same way.

For me the coolest feature of PersistentObject is, that the component does not require you're ORM enabled classes to inherit from a certain base to allow your objects to be stored in a database (made persistent).

This new object gives you a "wapper" of sorts to make any of the pre-existing objects in your application persistent. Check out the article for more.

This is a follow up to a question posted by Sam in my DB-2-MDB2 post. The question was if you can reuse an exisitng database connection you've already established and not have MDB2 creating a second connection.

He gives two different methods, one for persistent connections and the other for non-persistent ones - including some code.

The reason behind using persistent connections is of course reducing number of connects which are rather expensive, even though they are much faster with MySQL than with most other databases.

They go on to talk about:

• issues with the number of active connections that could come up
• the use of too many connections at once
• why persistent connections are disabled in the new mysqli extension