Call Ajax from PHP

Question

I want to do an ajax call in a php file. (the final goal is to get a localStorage). If I have well understood i begin with a start session in the php.

<?php
session_start();
?>

Then, ajax call of another php file.

<script>
    src="jquery.js";
    var variableToSend = 'foo';
    $.ajax({
        type: "post",
        async : false,
        url: "/login_getStorage.php",
        data: { variable: variableToSend }
    });
</script>

In this file php login_getStorage.php I have only

<?php
$_SESSION['toto'] = "titi";

If I have well understood, the variable $_SESSION['toto'] should be initialized everywere with "titi"

So in the main file :(so after script)

<?php
echo($_SESSION['toto'] );

I thought it will display 'titi'. But I have the error PHP Notice: Undefined index: toto

It seems that my ajax call is not done

How can we do to do this ajax call ?

Best regards.

I *think* the problem is probably that the first PHP script is done, dusted and finished before the Ajax call takes place - so if the session variable is set in the script called over Ajax you'll not see it in the first script until you reload the page. [This QA](https://stackoverflow.com/questions/13840429/what-is-the-difference-between-client-side-and-server-side-programming) might help explain the situation better. — CD001, Dec 17 '19 at 10:46
What you'd generally do in the script you're calling over Ajax is echo out a JSON representing the state change, which you use in the `success()` callback to do what you need to do (set what you want in `localStorage`); you can't *go back* to PHP at that point as it runs on the server not the client. — CD001, Dec 17 '19 at 11:01
It depends on what *exactly* you're trying to do - [this QA](https://stackoverflow.com/questions/5004233/jquery-ajax-post-example-with-php) should cover the specifics of using Ajax/jQuery. As an aside though, you realise there's a typo in your code here? ` — CD001, Dec 17 '19 at 11:20
To answer better what I want to do : In the beginning of php (session_start), I have something in the local storage. So I want to retreive this. So as it is impossible to access to localStorage inside php I try to do an ajax call. — C Morell, Dec 17 '19 at 11:31
What do you want PHP to do with that data from `localStorage` ? I've got a feeling you're sort of approaching the problem backwards - but I could be wrong. — CD001, Dec 17 '19 at 11:41

score 2 · Answer 1 · answered Dec 17 '19 at 11:41

2

In this file php login_getStorage.php I have only
<?php
$_SESSION['toto'] = "titi";

You need to call session_start() before you can use $_SESSION['toto'] in any PHP file.

Your Ajax call is probably working just fine, but since you are editing the contents of a session that doesn't exist, it isn't having the effect you want.

answered Dec 17 '19 at 11:41

Quentin

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Thank you, session_start is needed but unfortunately it does not work. – C Morell Dec 17 '19 at 13:37

score 0 · Answer 2 · answered Dec 17 '19 at 14:01

PHP is run on the server BEFORE any of the javascript is parsed.

There are a few questions:

Did you include the jquery library?
Are there any JS errors?

Try to add the success to your ajax:

success: function(data){ 
    // when success
}

Your PHP is run before your ajax call so the value doesn't exist on page load.
Instead of assigning a value on the PHP page you can also return a value.

<script>
    src="jquery.js";
    var variableToSend = 'foo';
    $.ajax({
        type: "post",
        async : false,
        url: "/login_getStorage.php",
        data: { variable: variableToSend },
        success: function(data){ 
           // when success display data 
           alert(data); // alert the session value
        }
    });
</script>

And then your login_getStorage.php:

<?php
session_start();
$_SESSION['toto'] = "titi";
echo $_SESSION['toto'];

Call Ajax from PHP

2 Answers2