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Most of the hosting companies are giving you nowadays option to use PHP 5.4 or 5.5, instead of 5.3.
The minimum PHP version that you need is 5.3.7, and I am sure that they have it there.
They might have older XOOPS version for installation, but if you have access to FTP, then you can upgrade your installation to XOOPS 2.5.6, by simply overwriting the files and running Upgrade.
I assume, you have full access to phpMyAdmin there, right?