Ensure displaying PHP Manual function page for PHP function symbols

Summary:
Some PHP functions have the same name as extension or class.
php.net prefers them over functions.

Test Plan:
http://www.php.net/hash
http://www.php.net/function.hash
http://www.php.net/function.hash_final

Reviewers: epriestley

Reviewed By: epriestley

CC: aran, epriestley

Differential Revision: https://secure.phabricator.com/D1977

src/applications/diffusion/controller/symbol/DiffusionSymbolController.php

@@ -68,7 +68,7 @@ final class DiffusionSymbolController extends DiffusionController {
         if ($request->getStr('type') == 'function') {
           if (in_array($this->name, idx(get_defined_functions(), 'internal'))) {
             return id(new AphrontRedirectResponse())
-              ->setURI('http://www.php.net/'.$this->name);
+              ->setURI('http://www.php.net/function.'.$this->name);
           }
         }
       }