mysql_connect() function in PHP's MySQL interface (which for reference maps to mysql_real_connect() function in MySQL C API) has a $client_flags parameter since PHP 4.3.0. This parameter is barely known and almost always overlooked but in some cases it could provide a nice boost to your application.
There's a number of different flags that can be used. We're interested in a specific one, MYSQL_CLIENT_COMPRESS. This flag tells the client application to enable compression in the network protocol when talking to mysqld. It reduces network traffic but at the cost of some CPU time: server has to compress the data and client has to decompress it. So there's little sense in using it if your Web application is on the same host as the database.
When the database is on a dedicated server then compression essentially means trading CPU time (on both server and client) for network time. …
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