PHP: xml_parse replaces entities and "?" character

How can I describe something I can't quite put my finger on? I have a module for RSS reading "magpierss" it uses xml_parse() and after extensive troubleshooting all I can come up with is that it removes certain entities like "?" character.

I haven't written this module myself but I have traced the code until the part uses xml_parse() and then the output is just replaced.

And to my disappointment this behavior exists on our production server only and not the local server. I have compared both php.ini file to search for any diff开发者_如何转开发erences but couldn't find anything.

Could anyone please direct on where to search exactly, i don't even know which direction to start from.

Thanks

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mb_string was enabled on the server and somehow it produces this unexpected behavior with xml_parse()