diff --git a/includes/common.inc b/includes/common.inc
index 7d0bf85..805e314 100644
--- a/includes/common.inc
+++ b/includes/common.inc
@@ -3820,6 +3820,28 @@ function drupal_flush_all_caches() {
 }
 
 /**
+ * Determine if a property exists on a given class. This function is used in
+ * place of property_exists() as it was only introduced in PHP 5.1.
+ *
+ * @param $class
+ * The class to check to see if a given property exists.
+ * @param $property
+ * The property to check to see if it exists on the given class.
+ *
+ * @return
+ * TRUE if the property exists, or FALSE otherwise.
+ */
+function drupal_property_exists($class, $property) {
+  if (is_object($class)) {
+    $vars = get_object_vars($class);
+  }
+  else {
+    $vars = get_class_vars($class);
+  }
+  return array_key_exists($property, $vars);
+}
+
+/**
  * Helper function to change query-strings on css/js files.
  *
  * Changes the character added to all css/js files as dummy query-string,