提交由preventDefalut（）阻止

Question

I am using ajax to make validation of login. I am having a problem with javascript e.preventeDefault(), when use it prevents submit and always shows validation empty field. When remove it is right but echo json data and doesnt shows validation messages inside dialog box, instead it redirects to url and echo the right json message. I think e.preventDefault prevents submit, is there any other way to put validation message inside dialog box insted of e.preventDefault() ?

$('#login_form').on('submit', function(e) {
    e.preventDefault(); 
    var username = $('#login_form input[name=sign_in_username]').val();
    var password = $('#login_form input[name=sign_in_pass]').val();
        $.ajax({
          url: "login.php",
          type: "POST",
          data: {username: username,
                 password: password
                },
          dataType: 'json',
          success: function(response) {

            if(response.status){ 
                           $(this).unbind('submit').submit()
            console.log(response);
            window.location = response.url;
               }
               else{
                   $('#invalid_content').html(response.msg);                                 
                }
            }
        });               
    });

login.php

if (((!isset($_POST["sign_in_pass"]) || !isset($_POST["sign_in_username"]) ) || trim($_POST["sign_in_pass"]) == "" || trim($_POST["sign_in_username"]) == "")) {
    echo json_encode(array('msg' => "Username or password are empty.", 'url' => "", 'status' => false));
    exit();
}
$rows = query("SELECT * FROM customers WHERE username = ?", $_POST["sign_in_username"]);

// nese form eshte bere submit
if ($_SERVER["REQUEST_METHOD"] == "POST") {
    if (count($rows) == 1) {
        $row = $rows[0];
        if (crypt($_POST["sign_in_pass"], $row["hash"]) == $row["hash"]) {
            $_SESSION["id"] = $row["id"];
            echo    json_encode(array('msg' => "Success.", 'url' => "index.php", 'status' => true));
        }
    } else {
        echo json_encode(array('msg' => "Username  or password invalid.", 'url' => "", 'status' => false));
    }
} else {
    echo json_encode(array('msg' => "Username  or password invalid.", 'url' => "", 'status' => false));
}

Answer 1

Your problem is not the e.preventDefault() . Your fields just don't match up, which is why they're empty.

Your data parameter should be: data: {sign_in_username: username, sign_in_password: password} .

The request your PHP script receives has the wrong field names in it.

In the future, for debugging purposes, on your PHP script, try var_dump($_POST); . This will give you an idea of what the request you received had in it.