php - 未定义的$链接？“mysqli_prepare() 期望参数 1 是..”

Question

$link 之前已定义，但代码会抛出上述错误

• if($stmt = mysqli_prepare($link, $sql)){

和

• mysqli_close($链接);

它可能会咬我的膝盖，但我没有看到问题......

function connect(){
   //connection to DB
   $link = mysqli_connect($this->database_socket, $this->db_username, $this->db_password, $this->db_name);
   if(mysqli_connect_error()){ 
       die(mysqli_connect_error());
   }else{
     return $link;
   }
}


// Processing form data when form is submitted
if($_SERVER["REQUEST_METHOD"] == "POST"){
 
...
    
    // Validate credentials
    if(empty($username_err) && empty($password_err)){
        // Prepare a select statement
        $sql = "SELECT id, username, password FROM users WHERE username = ?";
        
        if($stmt = mysqli_prepare($link, $sql)){
            // Bind variables to the prepared statement as parameters
            mysqli_stmt_bind_param($stmt, "s", $param_username);
            
...
    
    // Close connection
    mysqli_close($link);
}

标签： phpmysql