diff --git a/core/includes/bootstrap.inc b/core/includes/bootstrap.inc
index d11e608..cc1305b 100644
--- a/core/includes/bootstrap.inc
+++ b/core/includes/bootstrap.inc
@@ -26,6 +26,11 @@
 const DRUPAL_MINIMUM_PHP = '5.4.5';
 
 /**
+ * Suggested version of PHP.
+ */
+const DRUPAL_SUGGESTED_PHP = '5.6.10';
+
+/**
  * Minimum recommended value of PHP memory_limit.
  *
  * 64M was chosen as a minimum requirement in order to allow for additional