Different way to d XMLWriter::writeRaw()

Question

I use a PHP class called healthvaultphp which uses XMLWriter::writeRaw().
While my development server had PHP 5.2, when trying to "go live", I found out the production server has PHP 5.1.6, and won't be upgrdaded in the enar future.

True, this is my fault not to verify the exact version, but the question is what can be the solution in the current situation.

XMLWriter was included inside PHP since PHP 5.2.0, and in any case, it is not a "Pure" PHP class, so I can't just grab the PHP code and implement it myself.

Does anyone has an idea what should be the simplest solution for such a case ?
Is there an equal class I can use instead of the XMLWriter, or even just to replace the writeRaw() call ?

Thanks, Shushu