diff --git a/app/common.php b/app/common.php
index 89994e5..5e7750e 100644
--- a/app/common.php
+++ b/app/common.php
@@ -57,10 +57,11 @@ function checkToken($token): array
 
 /**
  * 获取随机字符
- * @param $length
+ * @param int $length
  * @return string
  */
-function generate_random_str($length = 8) {
+function generate_random_str(int $length = 8):string
+{
     $characters = '0123456789abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ';
     $username = '';