variable in jquery function is null - php

Question

I am having a problem with seeing one of my variables on a webpage. Here is what I have so far.
$(document).ready(function() {
$(function() {
$("#CheckID").click(function() {
// submit ajax job and display the result
var id = '$("#ID").val()'
$.ajax({
type: "POST",
url: "test_wID.php",
data: "id",
success: function(data) {
$('#rightselection').html(data)
}
});
});
});
});
This is the jquery function I am using to take an ID entered into a form and use that ID with a bash script.
Here is the php.
<?php
//Get the ID from the HTML form and use it with the check chunk script.
$id = $_POST['ID'];
if (is_null($id)){
echo "$id is null";
}
echo "Selected test Game ID: ".$id;
//print shell_exec('/opt/bin/tester $id');
?>
I commented out the script because the variable is returning null, at this point I am just trying to make sure that I get the ID.
For completeness here is the form I'm using.
print "<p><h3>ID: <input type=\"text\" id=\"ID\" /></h3></p>";
#print "<br>";
print "<p><button id=\"CheckID\">Check ID</button></p>";
When i click the button I get the message in my div that the variable is null. So my question is am I missing something in the declaration? How is it that the var id is null?
Thanks for any help provided.

Answer 1

You should consider changing your jQuery code to:
$.ajax({
type: "POST",
url: "test_wID.php",
data: {id: $("#ID").val()},
success: function(data) {
$('#rightselection').html(data)
}
});

Answer 2

You mixed up strings and variable references at two points.
First, the statement var id = '$("#ID").val()' assigns just a string to your if variable and not the return value of the jQuery call. So just remove the ' here.
Second, the data parameter you're giving to the ajax() call again consists just of a string "id" and not the respective value. Here you need to change to {'id': id}.
So after correcting everything, your code should look like this:
$(document).ready(function() {
$("#CheckID").click(function() {
// submit ajax job and display the result
var id = $("#ID").val();
$.ajax({
type: "POST",
url: "test_wID.php",
data: {'id': id},
success: function(data) {
$('#rightselection').html(data);
}
});
});
});
Sidenote: Try to put all ;, where they belong. This prevents some errors, which can be hard to track!
EDIT
As pointed out in the comment by #FlorianMargaine you only need one wrapper not two around your code.

Answer 3

Firstly, the two following snippets are equivalent:
$(document).ready(function() {
});
// Is equivalent to:
$(function() {
});
So your code does the same as:
$(document).ready(function() {
$(document).ready(function() {
});
});
Plain useless, right?
Secondly, this line is plain wrong:
var id = '$("#ID").val()';
You're passing a string to the id variable. $('#ID').val() is not evaluated. This is the equivalent of doing this in PHP:
$id = '$_POST["id"]';
Which is just wrong, right?
You want this:
var id = $('#ID').val();
By the way, this variable naming could be improved, the same goes for the HTML ID.
Thirdly, you're doing the same mistake in the data option of $.ajax:
data: 'id'
You're just passing a string to the data option. You want the value of the id variable.
Then, if you absolutely want a string, I don't recommend it. jQuery expects a special kind of string. You better pass an object. Like this:
data: {
id: id
}
Do you see why the variable naming is wrong? You can't differentiate the property from the value. If you had done the following:
var idValue = $('#ID').val();
You could use this:
data: {
id: idValue
}
Which is way more readable.

Answer 4

In your $.ajax call you need to do:
data : { id: id }

Answer 5

If you want to pass parameters in an AJAX call you need to pass a string similar to the GET string you see in urls. So something like: d=123&name=test
Change the line
var id = '$("#ID").val()'
To
var id = 'id=' + $("#ID").val();