PHP version fallback for "YiiRequirementChecker" has been added.

yii/requirements/YiiRequirementChecker.php

@@ -5,6 +5,11 @@
  * @license http://www.yiiframework.com/license/
  */
 
+if (version_compare(PHP_VERSION, '4.3', '<')) {
+	echo 'At least PHP 4.3 is required to run this script!';
+	exit(1);
+}
+
 /**
  * YiiRequirementChecker allows checking, if current system meets the requirements for running the application.
  *