Connection pooling in PHP

Question

Is it possible to cache database connections when using PHP like you would in a J2EE container? If so, how?

Answer 1

There is no connection pooling in php.
mysql_pconnect and connection pooling are two different things. There are many problems connected with mysql_pconnect and first you should read the manual and carefully use it, but this is not connection pooling.

Connection pooling is a technique where the application server manages the connections. When the application needs a connection it asks the application server for it and the application server returns one of the pooled connections if there is one free.

We can do connection scaling in php for that please go through following link: http://www.oracle.com/technetwork/articles/dsl/white-php-part1-355135.html

So no connection pooling in php.

As Julio said apache releases all resources when the request ends for the current reques. You can use mysql_pconnect but you are limited with that function and you must be very careful. Other choice is to use singleton pattern, but none of this is pooling.

This is a good article: https://blogs.oracle.com/opal/highly-scalable-connection-pooling-in-php

Also read this one http://www.apache2.es/2.2.2/mod/mod_dbd.html

Answer 2

Persistent connections are nothing like connection pooling. A persistent connection in php will only be reused if you make multiple db connects within the same request/script execution context. In most typical web dev scenarios you'll max out your connections way faster if you use mysql_pconnect because your script will have no way to get a reference to any open connections on your next request. The best way to use db connections in php is to make a singleton instance of a db object so that the connection is reused within the context of your script execution. This still incurs at least 1 db connect per request, but it's better than making multiple db connects per reqeust.

There is no real db connection pooling in php due to the nature of php. Php is not an application server that can sit there in between requests and manage references to a pool of open connections, at least not without some kind of major hack. I think in theory you could write an app server in php and run it as a commandline script that would just sit there in the background and keep a bunch of db connections open and pass references to them to your other scripts, but I don't know if that would be possible in practice, how you'd pass the references from your commandline script to other scripts, and I sort of doubt it would perform well even if you could pull it off. Anyway that's mostly speculation. I did just notice the link someone else posted to an apache module to allow connection pooling for prefork servers such as php. Looks interesting: https://github.com/junamai2000/mod_namy_pool#readme