Problem solved: php-mysql was not installed...

Thanks for the support anyway...

Turned on debugging in:
- PHP (Was allready on)
- include/common.php
- install/index.php

I still recieve a blank screen...

During the installation of XOOPS 2.5.1, after clicking next (To Check the Database) at the "Confirm Database Settings" step, the screen turns white and nothing further happens.
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confirm database settings
Database Hostname localhost
Database Username root
Database Name xoopsdb
Table Prefix XOOPS

<< restart from the beginning check database >>
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I am able to use the database with mysql:

#mysql -u root -p
mysql> use xoopsdb
Database changed
mysql> show tables;
Empty set (0.01 sec)
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Does anyone have an idea?