move $URI.php test higher up in error.php (phpweb bug #67871)

This test was below (way below) the $URI = strtolower($URI) line, so
when browsing to /manual/pt_BR/function.strpos we were looking for
/manual/pt_br/function.strpos.php which doesn't exist (on case-sensitive
filesystems).

Note: This is a quick fix... if it causes (significant) issues, we might
have to think of a more involved solution than shuffling the code up the
file by a few hundred lines.

Author: salathe

error.php

@@ -189,6 +189,17 @@
 if (is_numeric($URI)) {
     mirror_redirect("http://bugs.php.net/bug.php?id=$URI");
 }
+
+// ============================================================================
+// Redirect if the entered URI was a PHP page name (except some pages,
+// which we display in the mirror's language or the explicitly specified
+// language [see below])
+if (!in_array($URI, array('mirror-info', 'error', 'mod')) &&
+    file_exists($_SERVER['DOCUMENT_ROOT'] . "/$URI.php")) {
+    echo($_SERVER['DOCUMENT_ROOT'] . "/$URI.php");
+exit;
+    mirror_redirect("/$URI.php");
+}
 
 // Work with lowercased URI from now
 $URI = strtolower($URI);
@@ -485,15 +496,6 @@
     $URI = $uri_aliases[$URI];
 }
 
-// ============================================================================
-// Redirect if the entered URI was a PHP page name (except some pages,
-// which we display in the mirror's language or the explicitly specified
-// language [see below])
-if (!in_array($URI, array('mirror-info', 'error', 'mod')) &&
-    file_exists($_SERVER['DOCUMENT_ROOT'] . "/$URI.php")) {
-    mirror_redirect("/$URI.php");
-}
-
 // ============================================================================
 // Execute external redirect if a rule exists for the URI
 if (isset($external_redirects[$URI])) {