Are you using PHP-FPM? In such cases the PHP engine can be located into another server and accessed through an IP address. The address is configured in the web server config files and the php.ini file is in the remote server. You can probably use ini_set() by including a script in top of the others. Through .htaccess this is done like this:
php_value auto_prepend_file "/path/to/iniset.php"
Otherwise in PHP:
I would also check with hosting documentation to see if you can set the directives through a dedicated interface.
Do you mean with a dedicated interface a thing like cPanel?
Yes. Sometimes you can edit configuration files only through these forms. You can, also, try to write a custom php.ini file and save it into the document root, success however depends on hosting configuration: if it is allowed then it will override the defaults.
There's no Cpanel, Plesk or any other known inteface installed. It's possible but then the client has to pay an extra monthly fee for this. But I will advise them to do so either, because the documentation 'how to install' is with cPanel.
On that server requirements page I linked to it syas 'The following PHP commands should be enabled' where and how do I enable those?
I got a message back from the provider and it's indeed not possible to edit the php,ini file because it's not only used by my hosting package, but also by others. That kind of sucks! What happend with the part 'private' in VPS? :)
I will ask if I can create a custom php.ini file in my own dcucment root to override settings.
I'll close this thread,. I've arranged a VPS for them and I'll most definatley will come here at DW with questions related to this, because I never had to work with a private or dedicated server before. Oh, oh... the command line :-)