Issue #1414394 by marcingy, xjm: Fix upgrade check for D8 and php 5.3.

core/update.php

@@ -22,13 +22,26 @@
  */
 define('DRUPAL_ROOT', getcwd());
 
+// Exit early if running an incompatible PHP version to avoid fatal errors.
+// The minimum version is specified explicitly, as DRUPAL_MINIMUM_PHP is not
+// yet available. It is defined in bootstrap.inc, but it is not possible to
+// load that file yet as it would cause a fatal error on older versions of PHP.
+if (version_compare(PHP_VERSION, '5.3.2') < 0) {
+  print 'Your PHP installation is too old. Drupal requires at least PHP 5.3.2. See the <a href="http://drupal.org/requirements">system requirements</a> page for more information.';
+  exit;
+}
+
 /**
  * Global flag indicating that update.php is being run.
  *
  * When this flag is set, various operations do not take place, such as invoking
  * hook_init() and hook_exit(), css/js preprocessing, and translation.
+ *
+ * This constant is defined using define() instead of const so that PHP
+ * versions older than 5.3 can display the proper PHP requirements instead of
+ * causing a fatal error.
  */
-const MAINTENANCE_MODE = 'update';
+define('MAINTENANCE_MODE', 'update');
 
 function update_selection_page() {
   drupal_set_title('Drupal database update');