Only list supported PDO drivers in installer

[gsnedders]

Currently we always list both SQLite and MySQL in the installer, regardless of not of whether the PDO drivers are loaded. We ought to check whether the drivers are installed before giving them as an option (note that it is possible that neither are installed).

[skippy]

The extension_loaded() method is what we want, here.

[skippy]

Attached is a patch which detects the currently installed PDO drivers. It forcibly excludes SQLite2. If no (usable) drivers are available, tell the user. If one or more drivers are available, only display those in the db_type drop-down.

[ringmaster]

Fixed in r1331.

[elazar]

There is an issue with this patch. array_combine requires that each parameter contain at least one element. If no PDO drivers are installed, this causes the following error when loading the installer once the .htaccess file has been created:

Error: array_combine() [function.array-combine]: Both parameters should have at least 1 element /var/www/habari/system/classes/installhandler.php : Line 200

A check should be added to ensure that the return value of PDO::getAvailableDrivers() contains at least one element and display an appropriate error accordingly if that is not the case.

[skippy]

fixed in r1558. Thanks for catching the oversight, elazar!