You need to install the mysql dll separately, you download it mysql.com
See here: Installation on Linux Systems
PHP 4
The option --with-mysql is enabled by default. This default behavior may be disabled with the --without-mysql configure option. If MySQL is enabled without specifying the path to the MySQL install DIR, PHP will use the bundled MySQL client libraries.
Users who run other applications that use MySQL (for example, auth-mysql) should not use the bundled library, but rather specify the path to MySQL's install directory, like so: --with-mysql=/path/to/mysql. This will force PHP to use the client libraries installed by MySQL, thus avoiding any conflicts.
PHP 5+
MySQL is not enabled by default, nor is the MySQL library bundled with PHP. Read this FAQ for details on why. Use the --with-mysql[=DIR] configure option to include MySQL support. You can download headers and libraries from MySQL. [/quote]