使用AJAX发布和重定向后如何访问PHP变量？

Question

I'm making a login page in PHP where the user inputs a username. If the username is valid, the user is redirected to another page, where the username they used is printed. If the username is not valid, the page prompts them to enter a valid username and the page reloads.

My problem is in 'POSTing' the valid "username" variable from the login page to the page the user is redirected to.

I know that in my form tags from my login page, I can put:

<form action='pageToPostTo.php' method='POST'>

</form>

However, my problem with this is that, as soon as the user hits submit, this ALWAYS seems to redirect to pageToPostTo.php. As a result, if the username is invalid, I don't know how to avoid this redirection.

Instead, I used jQuery's ".ready" and ".click" to execute javascript code that verifies whether the username is valid when the user clicks "submit." If it's valid, then Ajax's "POST" method is called. If it's not valid, then the login page prompts and reloads.

function isValid(username) {
    return true;
}

$(document).ready(function () {

    $('input#submit').click(function (event) {

        event.preventDefault();

        if(isValid(username.value)) {
            postUser();
        }

        else {
            alert("Invalid Username");
            location.reload();
        }
    });
});

postUser() is shown below:

function postUser() {

    var username = username.value;

    $.ajax({
        url: 'pageToPostTo.php',
        type: 'POST',
        data: {getUsername: username}, // username = "danny"
        success: function(response) {
            alert(response);    // Outputs: "Your username is: danny"
            window.location.href = 'pageToPostTo.php'; // Outputs: "Your username is: Notice: Undefined index: getUsername..."
        }
    });
}

"alert(response)" within the "success" function of my Ajax post object properly evaluates $_POST['getUsername']. This shows me that my Ajax post is working perfectly.

THIS IS WHERE MY PROBLEM IS: As soon as I redirect to pageToPostTo.php, $_POST['getUsername'] stops evaluating and instead returns "Notice: Undefined index: getUsername".

Ajax's "post" method seems to work but the redirection is missing what Ajax "posted."

Is there a way to redirect to "pageToPostTo.php" after the Ajax "post" method executes, such that after the redirection, I can retrieve what has been posted by Ajax with $_POST['getUsername']?

If not, why not and what alternatives do I have to get the same functionality?

Previously I was using localStorage.setItem("usernameStorage", username.value) and localStorage.getItem(...) to transfer variables between by php files. Are there any disadvantages to doing it this way?

Snip from my loginPage.php:

<form name="login">
    <p>Username: <input type="text" id="username" ></p>
    <input type="submit" id="submit">
</form>

pageToPostTo.php:

<?php
    $validUser = $_POST['getUsername'];
    echo "Your username is: " . $validUser;
?>

PS The function to verify whether a username is valid must be in JavaScript.

Answer 1

You just have to start using developed solutions in this case. Like a work around i propose you to use $_SESSION to store your data while you transfer it between the files. In your case: After User login, program validate and if it is success, save it in

$_SESSION['user_id'] = $user_id

after that you make a redirection to your file: pageToPostTo.php: and first of all check if user_id exist in session, if not -> redirect to login page , if exist, assign value to $var and do what you need to do with that.

You have to execute your login php at the same page, and make the redirection ONLY in case if validation was successful. that's is addition to my answer.

Answer 2

You can use form submit instead of button click in jQuery.
Example :
Here is your html form:

<form action='pageToPostTo.php' id="action-form" method='POST'></form>

Modified JQuery Script :

$("#action-form").submit(function(){
  if(!isValid(username.value)) {
    alert("Invalid Username");
    return false;
  }
});

In that way, If user name is valid then it will automatically redirect on 'pageToPostTo.php'. There is no need to hit ajax request.