My AJAX post variable is not getting to my PHP

Question

I have made an AJAX function, and it actually works, but I can't get the variable with PHP. This is my code:

// Validate signup
function validateSignup(){
    // Get values
    var username = document.getElementById("pm_username").value;
    var email = document.getElementById("pm_email").value;
    var password = document.getElementById("pm_password").value;
    // Make new object
    var data = {};
    // Make array from object
    data['data'] = [];

    // If values are not empty...
    if(username !== "" || email !== "" || password !== ""){
        data['data'].push(email, username, password);
        // Convert data to JSON string and make new XMLHttpRequest
        var json = JSON.stringify(data['data']), xhr = new XMLHttpRequest();

        // Page to open
        xhr.open("POST", "ajax/signup.php", true);
        // Set header to POST
        xhr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
        // Send values
        xhr.send(json);
        console.log(json);

        xhr.onload = function(){
            console.log(xhr.responseText);
        }

    }else{ // ...or throw new exception
        throw("Some thing was not filled in!");
    }
}

It works, but I don't know how I should get the JSON variable in my PHP. This is my PHP code (simple):

<?php

$json = $_POST['json'];
echo $json;
echo "Test";

?>

It works, because the "Test" echo is being displayed in the console. However, I am getting this back:

<br />
<b>Notice</b>:  Undefined index: json in <b>G:\usbwebserver\root\pokemonisle\ajax\signup.php</b> on line <b>3</b><br />
Test

That means that the $_POST['JSON'] is not being recognised. I am not using jQuery because I want to learn how XMLHttpRequests work.

You post array keys that have `email`, `username`, `password` not `json`. Try `$email = $_POST['email'];` — Bora, Jun 20 '14 at 09:12
$_POST says array(0)... And should I not do $_POST['json'] since I post a JSON string? — user3759496, Jun 20 '14 at 09:15

score 0 · Answer 1 · edited Jun 20 '14 at 11:05

Your POST array doesn't contain a field named json.

Try the following:

<?php 
var_dump($_POST);
?>

to check which fields you are getting.

To prevent the error you could try:

<?php
if(isset($_POST['json']))
{
    $json = $_POST['json'];
    echo $json;
}
?>

and similarly to get other variable you could use:

<?php
if(isset($_POST['username']))
{
    $username = $_POST['username'];
    echo $username;
}
?>

score 0 · Answer 2 · edited May 23 '17 at 10:32

0

You do not send a post data named 'json', so you can't get it on server side.

Try to stringify your data object like

var json = "json="+JSON.stringify(data['data']);

and get it as

$json = $_POST['json'];

You can check out this link. Send POST data using XMLHttpRequest

edited May 23 '17 at 10:32

Community

1
1

answered Jun 20 '14 at 09:19

ymutlu

6,585
4
35
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score 0 · Answer 3 · edited Jun 20 '20 at 09:12

A string is generated of the array when you "JSON.stringify(data['data'])" it.

For example the output of this

var name ="abc";
var surname ="xyz";
var data ={};
data['data']=[];
data['data'].push(name, surname);
var json = JSON.stringify(data);
console.log(json);

shall be

{"data":["abc","xyz"]}

The $_POST['json'] should give you what .???

The $_POST['name'] (in a form for example) gives you the value of the field username.

My AJAX post variable is not getting to my PHP

3 Answers3