Undefined Variable $_POST['data'] PHP /Ajax jquery

Question

Hello guys that is not normal :) !!

foo.php

     <?php 
         if (isset($_POST['data']))
         $stringData = $_POST['data'];
         $file = "ciao.txt"; 
         $fh = fopen($file, 'w') or die("can't open file");
         fwrite($fh, $stringData);
         fclose($fh); 

         ?>

file.js

    function WriteToFile() {
        var dataa = "foo bar";
     $.post("foo.php", {data: dataa}, function(result){ alert("ciaoooo!!");}            
           , "json");
    }

this is the error and i can't write on my file.txt

Notice: Undefined variable: stringData

I tried also with that kind of function

function WriteToFile() {
    var data = "foo bar";
$.ajax({
    url: 'foo.php',
    type: 'POST',
    data: { 'data' : 'data'},
    success: function() {
        alert('the data was successfully sent to the server');
    }
});

but the result is the same!! Anyone have some idea???

you shouldn't have data in quotes as the value of the data property, or it will just literally pass the string 'data' — thescientist
– thescientist, Commented Jul 27, 2012 at 17:06
If the $stringData variable is not defined. That means that the isset($_POST['data']) conditional did not execute, which means you have no post data. — Mike Brant
– Mike Brant, Commented Jul 27, 2012 at 17:08

nickb · Accepted Answer · 2012-07-27 17:07:59Z

4

You're missing curly brackets:

if (isset($_POST['data'])) {
         $stringData = $_POST['data'];
         $file = "ciao.txt"; 
         $fh = fopen($file, 'w') or die("can't open file");
         fwrite($fh, $stringData);
         fclose($fh); 
 }

Without them, you essentially have this:

 if (isset($_POST['data'])) {
         $stringData = $_POST['data'];
 }
 $file = "ciao.txt"; 
 $fh = fopen($file, 'w') or die("can't open file");
 fwrite($fh, $stringData);
 fclose($fh);

Which explains why you're getting undefined $stringData, because the POST is not being executed properly.

Note that this doesn't solve your JS / jQuery problems. For that, see the other answers.

answered Jul 27, 2012 at 17:07

nickb

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Comments

raidenace · Accepted Answer · 2012-07-27 17:44:04Z

2

Ok, I think here's what is happening:

The code you have posted (foo.php/file.js in example 1) is correct, and will work without issues. I am not sure if you are trying to hit the foo.php URL directly in the browser. In that case there is nothing posted, so $stringData will be undefined, and it will throw the notice you are seeing.

What you need to do is: 1. Include the file.js script in an HTML file. 2. Make sure you have included jquery library 3. Make sure that the PHP (foo.php) file path is correct in $.POST 4. Call WriteToFile() on the HTML body onLoad function

Here is a sample HTML which should work (update path to foo.php if needed)

<script src ="http://ajax.googleapis.com/ajax/libs/jquery/1.7/jquery.min.js"></script>
<script>
function WriteToFile() 
{
    var dataa = "foo bar";
    $.post("foo.php", {data: dataa}, function(result){ alert("ciaoooo!!");}, "json");
}
</script>

answered Jul 27, 2012 at 17:44

raidenace

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4 Comments

Edivad Over a year ago

i did all the 4 steps that you said before but is still not working, is like if the value data that i send by POST method is not formatted in a good way!!

raidenace Over a year ago

hmm...strange, cause I copy-pasted the very same code sample you had and it works for me. Can you paste all three file codes you have, the PHP,JS AND the HTML used to call it? I think this is something really small that we are missing..

Edivad Over a year ago

I made some test and i discovered that is like when i open the file.html he doesn't call the php file, because i can write on ciao.txt only if I launch the php file

Edivad Over a year ago

Hey i looks like when i test it work in local but when i deploy it on the serever doesn't want to work....

Oscar Jara · Accepted Answer · 2012-07-27 17:07:44Z

0

Don't use quotes at this point:

data: { 'data' : 'data'},

replace it with:

data: {data : data},

Also, in the first code snippet you need brackets, correct it like this:

if (isset($_POST['data'])) {
  /* Your code here */
}

answered Jul 27, 2012 at 17:07

Oscar Jara

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Comments

thescientist · Accepted Answer · 2012-07-27 17:08:06Z

0

I think you want something like this:

function WriteToFile() {
    var data = "foo bar";
    $.ajax({
    url: 'foo.php',
    type: 'POST',
    data: data,
    success: function() {
        alert('the data was successfully sent to the server');
    }
});

answered Jul 27, 2012 at 17:08

thescientist

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1 Comment

Edivad Over a year ago

I tried boths of the solution but i still have the same problem but if i check $_POST with if (isset($_POST['data'])) i dont have the NOTICE but i can't write into the file.

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