md5哈希在PHP中引发错误

md5哈希在PHP 中引发错误

（！）注意：在中使用未定义的常量md5-假定为"md5"C： 第22行的''wamp''www''sva2''php''register.php调用堆栈#时间记忆功能位置1 0.0115 381992｛main｝（）。。''register.php：0

    <?php
require 'ChromePhp.php';
$dbhost = 'localhost';
 $dbuser = 'root'; // $dbuser = 'root'
 $dbpass = '';     // $dbpass = ''
 $conn = new mysqli($dbhost, $dbuser, $dbpass, 'ss');
// Check connection
 if ($conn->connect_error) {
    ChromePhp::log("Connection failed: " . $conn->connect_error);
} 
 $username = $_GET['username'];
 $password = $_GET['password'];
 $confirmpassword = $_GET['password_confirm'];
 ChromePhp::log($username);
 //ChromePhp::log($password);
 if($username != "")
 {
 $mdsh = $username.'';
 $mdhash = md5($mdsh);

   }
$conn->close();
?>