jQuery variable to php variable - php

Question

i have a problem when it comes to retrieving value from jQuery to php.i was able to get the value of my select and pass it to my php but i can't pass it back to php.
here is the code...
<script>
$(document).ready(function()
{
$("select#months").change(function(event)
{
var m=$(this).val();
alert(m);
});
});
</script>
<div>
<select id="months">
<option value='00'>Month...</option>
<option value='01'>Jan</option>
<option value='02'>Feb</option>
<option value='03'>Mar</option>
<option value='04'>Apr</option>
</select>
<select id="years">
<?php
for($yr=10; $yr<=$year; $yr++)
{
echo "<option value='".$yr."'>".$years[$yr]."</option>";
}
?>
</select>
</div>
now i have to get the m variable from the jQuery code and echo it on my php.

Answer 1

You need to post or get the page again, passing "m" as a parameter and reading it inside php.
Php and jquery can communicate with each other only using http posts/gets, cause they run on two different computers (php on your server, jquery on your users browser)
Unfortunately, to answer this question completely would mean teaching client-server from the basics.

Answer 2

The jQuery code will run on your user's browser. You need to send m via POST (or GET) to your PHP script upon change.
Try this:
$(document).ready(function()
{
$("select#months").change(function(event)
{
var m=$(this).val();
$.ajax({
type: 'POST',
url: "http://example.lan/your.php",
data: {m: m},
success: function(){alert("updated")}
});
});
});
and on your PHP code, do something about m if it is set:
<?php
if (isset($_POST['m'])) {
// do stuff with M here
}
?>

Answer 3

PHP and Javascript may appear in the same file, but they are far from being executed by the same machine. For example, take this simple script :
<?php
$foo = "Hello world!";
?>
<div id="mydiv"><?php echo $foo; ?></div>
<script type="text/javascript">
$(function() { alert( $('#mydiv').text() ); });
</script>
When you access this script from your browser, the server actually only parse this :
<?php
$foo = "Hello world!";
echo $foo;
Because everything else is not PHP, thus not processed by the engine (skipped at parsing time). Therefore, the document that is uploaded by the server to your browser is
<div id="mydiv">Hello world!</div>
<script type="text/javascript">
$(function() { alert( $('#mydiv').text() ); });
</script>
As you see, at this point, there is no PHP at all in what's outputted by the server (what is received by the client), so there is no way that you can reference anything PHP at that point. The only way you can do this is by calling the same script again! (or any other PHP script)
PHP may receive parameters from external sources via $_GET and $_POST. Thus, modifying our code would be like
<?php
if (isset($_GET['foo'])) {
$foo = $_GET['foo']; // we received our param like
// '?foo=Hi!` from the HTTP request
} else {
$foo = "Hello world";
}
?>
<div id="mydiv"><?php echo $foo; ?></div>
<form action="" method="get">
<input type="text" name="foo" value="" />
<input type="submit" name="submit" />
</form>
<script type="text/javascript">
$(function() { alert( $('#mydiv').text() ); });
</script>
And you can communication in both directions. For XHR with jQuery, there is no need to send a whole bunch of HTML with the query, we need to modify the source a little:
<?php
if (isset($_GET['foo'])) {
echo "Message got : " . $_GET['foo'];
exit; // do not execute any more code from now
} else {
$foo = "Hello world";
}
?>
<div id="mydiv"><?php echo $foo; ?></div>
<script type="text/javascript">
$(function() {
alert( $('#mydiv').text() );
// note : assuming the code is in file "example.php"
$.get('example.php', {foo: "Hi!"}, function(data) {
alert(data); // will show "Response got : Hi!";
});
});
</script>
In the last example, the file is parsed and processed twice by the server, the code is actually executed in this order :
the browser makes a first query to the PHP script
the server parse the file and sends the HTML,
the client receives the HTML
the Javascript code is executed
alert : "Hello world!"
create and send a GET XHR with parameter foo=Hi!
the server receives another request and parse the file
the $_GET['foo'] argument is found
echo "Response got : Hi!"
the client receives the XHR response and invoke the callback function
alert : "Response got : Hi!"
Now, this last example may seem a bit more complicated, but really as simple as the other code :
<?php
$dataFile = 'data.txt';
if (isset($_POST['text'])) {
file_put_contents($dataFile, $_POST['text'];
echo "Saved!";
exit;
} else if (file_exists($dataFile)) {
$text = file_get_contents($dataFile);
} else {
$text = '';
}
?>
<a id="lnkSave" href="example.php">Save</a>
<script type="text/javascript">
var text = '<?php echo addslashes($text); ?>';
$(function() {
$('<textarea></textarea>').attr('id', 'text').appendTo(document).val(text);
$('#lnkSave').click(function() {
$.post($(this).attr('href'), {text:$('#text').val()}, function(data) {
alert(data);
});
});
});
</script>
I'll let you figure this one out; what it does and how it works.