Is there a safe way of allowing users to add their own PHP to my server?
<p>I'm developing a platform that allows users to create apps using PHP. Is there any safe way of allowing users to do this? Can you restrict use of functions that could damage existing source code or the server in anyway? I only want them able to use basic functions, and give them access to 1 database. This must be possible, because of the existence of shared servers, ran by many users. 
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<p>Any advice?  </p>
