As stated above, when symlinking to a php file outside of the httpdocs directory Apache/php serves an empty file. However if I change the extension to html the file is served properly as an html document. This leads me to believe that it is not a permissions error but could be something related to the php configuration (could open_basedir be causing this?) or Apache.
Does anyone know what could be causing this behavior?
EDIT: For anyone wondering about this, the problem was cause by the php open_basedir restriction.
Turn on error reporting in PHP and check your PHP error log. 100% guaranteed that you had a fatal scripting or configuration error.