small refactoring + cleanup request

framework/web/Request.php

@@ -180,14 +180,13 @@ class Request extends \yii\base\Request
 	{
 		if ($this->_headers === null) {
 			$this->_headers = new HeaderCollection;
-			$headers = [];
 			if (function_exists('getallheaders')) {
 				$headers = getallheaders();
 			} elseif (function_exists('http_get_request_headers')) {
 				$headers = http_get_request_headers();
 			} else {
 				foreach ($_SERVER as $name => $value) {
-					if (substr($name, 0, 5) == 'HTTP_') {
+					if (strncmp($name, 'HTTP_', 5) === 0) {
 						$name = str_replace(' ', '-', ucwords(strtolower(str_replace('_', ' ', substr($name, 5)))));
 						$this->_headers->add($name, $value);
 					}