commit 3a396312cc78c63c3acb19f0d5c9c452340650b9
Author: Pieter Frenssen <pieter@frenssen.be>
Date:   Tue Apr 1 11:59:07 2014 +0200

    1988780-13

diff --git a/modules/simpletest/drupal_web_test_case.php b/modules/simpletest/drupal_web_test_case.php
index a69d3af..5e04270 100644
--- a/modules/simpletest/drupal_web_test_case.php
+++ b/modules/simpletest/drupal_web_test_case.php
@@ -2529,12 +2529,7 @@ class DrupalWebTestCase extends DrupalTestCase {
         // Return the string.
         $value = count($parts) > 1 ? 'concat(' . implode(', \'"\', ', $parts) . ')' : $parts[0];
       }
-      // Use preg_replace_callback() instead of preg_replace() to prevent the
-      // regular expression engine from trying to substitute backreferences.
-      $replacement = function ($matches) use ($value) {
-        return $value;
-      };
-      $xpath = preg_replace_callback('/' . preg_quote($placeholder) . '\b/', $replacement, $xpath);
+      $xpath = str_replace($placeholder, $value, $xpath);
     }
     return $xpath;
   }