Fixes #579 Nested sub path parsing

Author: joelpittet

src/Saml2/Utils.php

@@ -722,8 +722,10 @@ protected static function buildWithBaseURLPath($info)
         if (!empty($baseURLPath)) {
             $result = $baseURLPath;
             if (!empty($info)) {
-                $path = explode('/', $info);
-                $extractedInfo = array_pop($path);
+                // Remove base path from the path info.
+                $extractedInfo = str_replace($baseURLPath, '', $info);
+                // Remove starting and ending slash.
+                $extractedInfo = trim($extractedInfo, '/');
                 if (!empty($extractedInfo)) {
                     $result .= $extractedInfo;
                 }