html连接数据库php不知道什么原因报错

Fatal error: Uncaught Error: Call to undefined function check_param() in D:\phpstudy_pro\WWW\webces\login.php:10 Stack trace: #0 {main} thrown in D:\phpstudy_pro\WWW\webces\login.php on line 10


$con=mysqli_connect("127.0.0.1","root","12345","web1"); //连接数据库，且定位到数据库web1
if(!$con){die("error:".mysqli_connect_error());} //如果连接失败就报错并且中断程序
$user=$_POST['user'];
$pass=$_POST['pass'];
if($user==null||$pass==null){
    echo "";
    die("账号和密码不能为空!");
}
if(check_param($user)==true&&check_param($pass)==true){
  $sql='select * from test where user='."'{$user}'and password="."'$pass';";
  $res=mysqli_query($con,$sql);
  $row=$res->num_rows; //将获取到的用户名和密码拿到数据库里面去查找匹配
  if($row!=0)
  {
      echo "
登录成功，欢迎您 {$user}！
";
  }
  else
  {
      echo "用户名或密码错误";
  }
}
?>


html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Documenttitle>
head>
    <body style="background-color:#0066CC">
        <h2 align="center" style="color: white">管理后台登录h2>
        <form align="center" action="login.php" method="post" enctype="multipart/form-data">        
            <p style="width:100%;height:30px;display:block;line-height:200px;text-align:center;color:white;font-size:16px;">账号:<input type="text" name="user" value="" max="10">p>
            <p style="width:100%;height:30px;display:block;line-height:200px;text-align:center;color:white;font-size:16px;">密码:<input type="password" name="pass" value="" min="6" max="16">p>
            <p style="width:100%;height:30px;display:block;line-height:200px;text-align:center;"><input type="submit" name="submit" value="登录">p>
        form>
body>
html>

Fatal error: Uncaught Error: Call to undefined function check_param() in D:\phpstudy_pro\WWW\webces\login.php:10 Stack trace: #0 {main} thrown in D:\phpstudy_pro\WWW\webces\login.php on line 10

check_param 没有定义。