[TYPO3-project-formidable] How to demask special characters in beforeInsertion PHP-Code?

[Hauke Hain]

Hi,

I want to do something like this in a beforeInsertion:
str_replace('ß', 'ß',$aData)

This does not work, because the "ß" is invalid in XML.

The whole php-code is in a <![CDATA[ ]]> so I don't know how to demask it in 
a way PHP will find and replace the "ß".

Do you have any idea?