14 August 2006
MySQL Connection Management in PHP
Posted by Mikhail Esteves under: LAMP; Tips .
Before I start the discussion on connecting to MySQL servers via PHP, it’s worth pointing out that the relative cost of connecting to a MySQL database, versus connecting to a PostgreSQL or Oracle installation, is very, very low. However, the fact that connecting to a MySQL resource is inexpensive does not mean that connection resources can be abused. Anyone who has ever seen the dreaded “Too many connections” error which occurs when MySQL attempts to service more connections than the number of concurrent connections afforded by the max_connections configuration variable, knows what I am talking about.
Connecting to a MySQL resource, while inexpensive, requires PHP to issue a call to the mysql client API via mysql_connect(). Passed as variables to this function are the connection arguments for the database host, user, password, etc. Once the MySQL database server has received the connection information, it will either return a success value, or a failure. Upon failure, the mysql_error() function can be used to determine what went wrong during the connection attempt (typically user credential problems or the max connections issue).
So, where, you ask, is the problem? Well, the issue that I commonly see is that connections are made to MySQL resources when they do not need to be made. But, you say, almost all web applications serve dynamic content, so therefore doesn’t dynamic content virtually require a connection to a database be made?
