从json数组中检索消息

Question

I want to check the username availability while users register. I am working on the front end. The backend code was given to me.

These are the php code in signup.php

if (isset($_GET['chkusername']))
JSON_username_avail($_GET['chkusername']);

function JSON_username_avail($username) {
    $ret = array();
    print json_encode(validate_username($username, $ret));
    die();
}

function validate_username($username, & $retval_arr) {
    if ($username == NULL)
        $retval_arr['E_UserName'] = "NULL_USERNAME";
    else if (!username_validation($username))
        $retval_arr['E_UserName'] = "INVALID_USERNAME";
    else if (!data_not_exists("user", "username", $username, TRUE))
        $retval_arr['E_UserName'] = "USERNAME_EXISTS";
    return $retval_arr;
}

function username_validation($user) {
    $username = str_split($user);
    foreach($username as $i) {
        $i = ord($i);
        if ($i >= 48 and $i <= 57)
            continue;
        if ($i >= 65 and $i <= 90)
            continue;
        if ($i >= 97 and $i <= 122)
            continue;
        return FALSE;
    }
    return TRUE;
}


function data_not_exists($table, $field, $data, $CSense = FALSE) {
    $conn = connect_db();
    $data = filter_var($data, FILTER_SANITIZE_STRING);
    if ($CSense == TRUE)
        $sql = "SELECT * FROM ".$table.
    " WHERE ".$field.
    "='".$data.
    "'";
    else
        $sql = "SELECT * FROM ".$table.
    " WHERE upper(".$field.
    ")='".$data.
    "'";
    $result = mysqli_query($conn, $sql);

    switch ($result - > num_rows) {
    case 0:
        return TRUE;
        break;
    case 1:
        return FALSE;
        break;
    default:
        die("500 Internal Server Error: 122");

    } //switch

}

Now I dont know that much of php. I created a javascript function to send the username to the signup.php page for validation.

Here is my function

function submit_form() {
    var u = document.getElementById("username").value;
    $.post("signup.php", {
            "chkusername": u
        },
        function (data) {
            var x = data; //here i dont know how to get the return string. Whether it is NULL_USERNAME OR INVALID_USERNAME OR USERNAME_EXISTS.

        }, "json");
}

here i am getting the value of x as [object Object]. But i need to store the return message in variable x. I want to know whether it is NULL_USERNAME OR INVALID_USERNAME OR USERNAME_EXISTS. Kindly help me with that.

Answer 1

The username is POSTed but in the PHP you try to access it with $_GET, change to:

if (isset($_POST['chkusername']))
JSON_username_avail($_POST['chkusername']);

Also your validation logic doesn't look right, what if the username is valid and available? I would add an else clause and set a success variable:

function JSON_username_avail($username) {
    $ret = array();
    print json_encode(validate_username($username));
    die();
}

function validate_username($username) {
    $retval_arr = array('success' => false, 'message' => '');

    if ($username == NULL)
        $retval_arr['message'] = "NULL_USERNAME";
    else if (!username_validation($username))
        $retval_arr['message'] = "INVALID_USERNAME";
    else if (!data_not_exists("user", "username", $username, TRUE))
        $retval_arr['msessage'] = "USERNAME_EXISTS";
    else
        $retval_arr['success'] = true;
    return $retval_arr;
}

and the ajax:

if(!data.success){
    console.log(data.message);
} else {
    // valid and available
}