Ajax sending to variable to php undefined index

Question

I would like to display the variable num in the php page.

The error i am getting is as follows:

Notice: Undefined index: num in C:\xampp\htdocs\javas.php on line 4

PHP:

<?php 
$lol = $_POST['num'];
echo "$lol " ;
?>

HTML/Javascript:

<html>
<head>
<script language="JavaScript" type="text/javascript">
function ajax_post(){
// Create our XMLHttpRequest object
var hr = new XMLHttpRequest();
// Create some variables we need to send to our PHP file
var url = "javas.php";
var num = "lol";

hr.open("POST", url, true);
// Set content type header information for sending url encoded variables in the request
hr.setRequestHeader("Content-type", "application/x-www-form-urlencoded");
// Access the onreadystatechange event for the XMLHttpRequest object
hr.onreadystatechange = function() {
    if(hr.readyState == 4 && hr.status == 200) {
        var return_data = hr.responseText;
        document.getElementById("status").innerHTML = return_data;
    }
}
// Send the data to PHP now... and wait for response to update the status div
hr.send(num); // Actually execute the request
document.getElementById("status").innerHTML = "processing...";
}
</script>
</head>
<body>
<h2>Ajax Post to PHP and Get Return Data</h2>

<input name="myBtn" type="submit" value="increment" onClick="javascript:ajax_post();">
<br /><br />
<div id="status"></div>
</body>
</html>

first of all show the dump what you are getting using print_r($_post); in your php code. Secondly correct me if i am wrong, i dont see that you are posting anything on this page. As i dont see any form — noobie-php
– noobie-php, Commented Dec 12, 2011 at 19:08

James · Accepted Answer · 2011-12-12 19:13:29Z

3

You have to send name/value pairs

hr.send("num=" + num);

answered Dec 12, 2011 at 19:13

James

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6 Comments

Watermark Studios Over a year ago

Was in the middle of posting the same thing...gotta have name/value pairs to pass.

fosho Over a year ago

how would i increment the value of num (first make it = 1) when the button is clicked?

James Over a year ago

Depends. If you need to store num somewhere (so the user can close his browser and come back later and the value of num is the same as it was before) then you would read the php value in the onreadystatechange func and set the javascript variable num = to that. If you just wanted num to be incremented for the duration of the session then you could change the send line to: hr.send("num=" + (++num));

fosho Over a year ago

this only increments once, i ould like to increment everytime the button is clicked

fosho Over a year ago

how do you set the value of num to the incremented value once it has sent

|

Brian Driscoll · Accepted Answer · 2011-12-12 19:13:56Z

0

One part of the issue here is that the parameter that you're posting is not properly serialized. The parameter string for a POST is similar to the query string for a GET request:

var1=foo&var2=bar

As it stands right now you're just sending a raw piece of data over (the value assigned to the variable num.

answered Dec 12, 2011 at 19:13

Brian Driscoll

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