CODEWITHSUNDEEP
phpjqueryajaxsessionsession-variables
Pike Man
Pike Man

Reputation: 353

Sending Data From A PHP Script Back To A JQuery AJAX Request

I am creating a web application and have the following problem.

In my application the user is working within a single page, they draw on a canvas. There is a single button called "Save". This takes the users ID and whatever they have created in the canvas and sends it to a database. This all works fine. The save function resemebles this:

$.ajax({
    url: "/database/write.php",
    type: "POST",     
    data: { 
        docName: name,
        docData: document_Data,
        docMode: "new"
    }, 
    success: function(html) {
        alert("Successfully Saved NEW document");
        set_Mode();
    },          
});

The above AJAX request does send the three values to the PHP script which then successfully creates a new document in the database, what i need to do now is change the application mode from saving a new document to editing the previously saved document. This means that when a user saves again, they will write to the same row, overwriting the previous version of the document.

When i send the data to the write.php it does write the data to the DB and the queries the database for that inserted document and retrieves its unique document ID. with that ID the application can the select that document and overwrite it. To retrieve the document ID from the query, i use the following code in write.php

write.php

$_SESSION['DOCUMENT_ID'] = $DOCUMENT_ID;

This $DOCUMENT_ID is the document ID retrieved from the SELECT query. The script then finishes and transfers control back to the main application page.

Back on the application page i try to retreive the value but it doesnt seem to work. I can retrieve $_SESSION values that were set when the user first accesses the application (id) but now values set by the write.php (DOCUMENT_ID) page. For example, below shows the function called after the AJAX request has been successful:

function set_Mode()
{
    var PHPvar_01 = <?php echo($_SESSION['id']); ?>;
    alert(PHPvar_01); //WORKS FINE

    var PHPvar_02 = <?php echo($_SESSION['DOCUMENT_ID']); ?>;
    alert(PHPvar_02); //DOES NOT WORK.          
};

How should i go about sending data retrieved from the PHP query script to the application, because $_SESSION does not seem to work here.

Thanks for any feedback.

Upvotes: 2

Views: 2196

Answers (4)

Keil
Keil

Reputation: 220

at the end of write.php :

echo json_encode(array('id'=>$_SESSION['id'], 'DOCUMENT_ID'=>$_SESSION['DOCUMENT_ID']));

in your ajax call :

success: function(data) {
    data = eval('('+data+')');
    alert("Successfully Saved NEW document");
    set_Mode(data.id, data.DOCUMENT_ID);
},

this should do the tricks !

Upvotes: 1

adeneo
adeneo

Reputation: 318192

You can't access variables on the server when the page is already loaded in the users browsers, other than with ajax.

You need to send something back, and in PHP all you have to do is echo something, and capture it in the success function of your Ajax call.

at the end of /database/write.php, do

echo $_SESSION['DOCUMENT_ID'];

and in JS

$.ajax({
    url: "/database/write.php",
    type: "POST",     
    data: { 
        docName: name,
        docData: document_Data,
        docMode: "new"
    }, 
    success: function(data) {
        alert("Successfully Saved NEW document");
        set_Mode();
        if (data == 'something') {
           //do something with the returned DOCUMENT_ID stored in the data variable
        }
    },          
});

Upvotes: 1

Michael Rose
Michael Rose

Reputation: 7820

Well, your PHP code gets executed only once upon the initial loading of the page. The server detects a request to your site, loads the PHP document internally, parses it and delivers it to the client.

Therefore, when the AJAX call returns, the entire PHP script is not executed again, because the user didn't request the whole page but only sent a single request to your write.php.

Your write.php script must return the $DOCUMENT_ID in some way, e.g. echo it directly, then the success handler in the jQuery AJAX call can access it via the handler's parameter (see jQuery documentation).

Upvotes: 1

gcochard
gcochard

Reputation: 11744

In your write.php, you should echo the $DOCUMENT_ID at the end of the page, and then your success function will receive that in the html argument. Then you should call set_Mode with the html variable that was passed into the success function.

You can't call set_Mode until after the page is loaded, and after you know the document ID. You are writing the document ID into the set_Mode function before you know it, in the initial page load.

Upvotes: 1

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