在Ajax中测试PHP响应

Question

I'm making a simple registration mechanism that stores username and password into a MySQL database. How it works:

1. User enters his data into textboxes.
2. The values get fetched and validation via JQuery script.
3. If the validation is passed, an Ajax call is made to a PHP file that then checks if the Username has already been taken. If it's taken, it does echo '0'. If not, it does echo '1' and inserts the values into the database.

4. Jquery then checks the response and does an appropriate action.

   $.ajax({
       type: "POST",
       url: "register.php",
       data: {usn:us, pwd: pw},
       cache: false,
       success: function(result){
           console.log(result);
           if (result=='1'){
               window.location = "next.php";
           }else{
               errorMessage= "Username taken. <br>";
               $("#regerrormsg").html(errorMessage);
           }
       }
       });
   

PHP:

include 'dbconnect.php';
    $us = $_POST["usn"];
    $pw = $_POST["pwd"];

    $tryus = $conn->query("SELECT Username from users WHERE Username='" . $us . "'");
    if ($tryus->num_rows == 0){
        echo '1';
        $conn->query("INSERT INTO users (ID, Username, Password) VALUES (DEFAULT, '" . $us . "', '" . $pw . "')");  
        session_start();
        $_SESSION["user"] = $us;
    }else{
        echo '0';
    }

Now, here's the weird thing. This pretty much works, except for one part. The query does indeed check if the username already exist and it does echo the appropriate value ('0' or '1'). I've tested this by logging the output in the javascript file. I've also checked my database and it never stores a duplicate user. But, for some weird reason, the window.location = "next.php"; is never executed, even when the value of the output is '1'. It always goes to the 'else' block. Any idea why this is happening? Thanks.

Answer 1

The best way to check backend responses is to use a REST Api Client. Postman is the most popular but I prefer Insomnia. Try it out, in my opinion it's a must have for front-end development.

Answer 2

Please change below code:

if ($tryus->num_rows == 0){
    echo '1';
    $conn->query("INSERT INTO users (ID, Username, Password) VALUES (DEFAULT, '" . $us . "', '" . $pw . "')");  
    session_start();
    $_SESSION["user"] = $us;
}else{
    echo '0';
}

to this:

if ($tryus->num_rows == 0){
    $conn->query("INSERT INTO users (ID, Username, Password) VALUES (DEFAULT, '" . $us . "', '" . $pw . "')");
    echo '1';
}else{
    echo '0';
}
exit();

Create session in variable in next.php file.

Change window.location = "next.php"; to document.location.href="http://your-site-url.com/next.php";