I tried to create a local API reference of the Zend Framework on our local network, with the PhpDocumentor tool. However, along the process it stops with the following error:

Of course PHP is installed in that prefix. It turns out that the error reporting of PhpDocumentor is quite poor, because this has nothing to do with environment variables at all. The PHP process simply ran out of memory, because it stores all parsed contents in memory. So to fix this problem it was sufficient to raise the memory_limit to a higher level in php.ini.