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cody_wes

make jquery value available in php

in Getting Started • 3 years ago

hello,

im quite new to jquery so i guess my questions are beginners questions.

I have a piece of jquery for getting the value of a slide button with html range.

I want the output in php available.

But for me it is not clear how jquery sets the output of the range slider in a variable?

And I also dont know how to post (like html $_POST) this variable to the php server?

what steps should I follow to get the value in a 'default' piece of code ?

code:

<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.0.0/jquery.min.js"></script>
<script>
$(function(){
      $("#range").change(function()
   {
   $("#value").text($(this).val());
      }
   );
});

</script>
</head>
<input type="range" min="1" value="3" max="4" name="value" id="range"/>
<span id="value"></span>
<br><br>
<?php
$offset = ob_get_clean();
print_r($offset);
?>
</html>

Replies(11)

watusiware

Re: make jquery value available in php

3 years ago

You can't. Because "that train already left the station".

When the page loads (let alone when the user interacts with it to change the value) PHP's job was long past done. The whistle blew, PHP went off-shift, went home for a cold beer.

On the other hand, if you can figure out how to get the value into the PHP code that generated the page, you may win the Nobel Prize for inventing a time machine! Not JUST a time machine, mind you - but spooky action at a distance in the past!

What is ob_get_clean()? I guess it's PHP. You need to find a PHP forum for PHP problems.

cody_wes

Re: make jquery value available in php

3 years ago

it is possible .

Look at this example and see how to get a javascript variable to php.

<?php
ob_start();
?>
<script type="text/javascript">
var d = 'hello world';
document.write(d);

</script>
<?php
$offset = ob_get_clean();
//print_r($offset);
echo '<br>'. $offset;
?>

This example works.

But because of my poor understanding of javascript and jquery I would like to figure out how the slider value from the example in the first post is transferred to a variable that is readable to put in document.write().

btw, the first example also needs ob_start() but I have not yet tested anything with that.

jakecigar

Re: make jquery value available in php

3 years ago

ob_get_clean does not get the output of javaScript. It gets the previous output of PHP.

$output is not "hello world". It is

<script type="text/javascript">
var d = 'hello world';
document.write(d);
</script>

which when finally shown on an html page looks like "hello world".

To get live values from javaScript to your server and then to a NEW php, you use AJAX or fetch.

That's the ONLY way to get a javaScript value into PHP.

JΛ̊KE

jakecigar

Re: Re: make jquery value available in php

3 years ago

This is an example that uses fetch…

<?php
if (isset($_POST['value'])) {
// sql update or write to file.
echo "updated";
exit;
}
?>
<html>
<head>
<script src="https://code.jquery.com/jquery-3.4.1.min.js"></script>
<script>
$(function() {
$("#range").change(function() {
$("#value").text($(this).val());
fetch("",{
method: 'POST',
body:new FormData(this.form),
}).then(r=>r.text()).then(console.log)
});
});
</script>
</head>
<form>
<input type="range" min="1" value="3" max="4" name="value" id="range"/>
<span id="value"></span>
<form>
</html>

JΛ̊KE

cody_wes

Re: make jquery value available in php

3 years ago

this answers the question.

But it raises more questions instantly because I can not get the output on the screen in the browser.

The comment is made in console.

Anyway thank you until here Jake.

jakecigar

Re: make jquery value available in php

3 years ago

Change

}).then(r=>r.text()).then(console.log)

}).then(r=>r.text()).then(putOnScreen)

and add to the bottom of the script.

function putOnScreen(x){
$("#value").text(x);
}

JΛ̊KE

cody_wes

Re: make jquery value available in php

3 years ago

I can't deny it works, but is not useful yet to me in this way.

1) removing exit results in a dump of the whole script.

2) placing the php code under the jquery does result in a script dump too.

what is the exact difference with the way php handles variables (compared to Jquery) and how can I have PHP pick up the value 1, 2, 3 or 4 ; in a way it is useful for other parts in the php script?

jakecigar

Re: make jquery value available in php

3 years ago

That's as good as you will get. If you want to use 2 php files you can avoid the exit.

JΛ̊KE

jakecigar

Re: Re: make jquery value available in php

3 years ago

You can change the echo to something more complex (like a JSON response) and plug in more variables with the fetch/ajax code. But it always has to work the same way.

JΛ̊KE

watusiware

Re: make jquery value available in php

3 years ago

I still think you are confused about locality and execution timeline.

- The browser requests a page from your server. Maybe because the user clicked on a link, or entered the page address in the browser's navigation bar.

- Your server receives the request, and passes the request to your PHP script that handles the page

1. The PHP script generates an HTML page and gives it to the server to send to the browser

2. The server sends the generated output to the browser

3. THE PHP SCRIPT IS DONE! Finished. No more. It's job is completed.

4. The browser loads the page, renders it on the screen, and runs the Javascript (if any) in the page.

5. The PHP code doesn't run in the browser. The Javascript code doesn't run on your server. They don't even run at the same time. Once the browser runs the Javascript the execution of the PHP script is history.

Some Javascript code can send some data to your server, using Ajax. It can send it to the same - or different - PHP script on your server. But it is a NEW execution of the script in either case.

Jake showed you how to use ONE script to perform TWO functions. If it is a page request, it sends the page. If it is an Ajax request, it uses the data received to update the database. But it is just a trick for using the SAME script to perform both functions. It would be better to just write two PHP scripts.

If your PHP script sends some data back from the Ajax request, then your Javascript code can use the data sent back in any way it might like. For example, to update some part of the page. Or not.

Your PHP script CANNOT directly change anything in the page in response to the Ajax request. The PHP script runs on your server, and has no access to Javascript variables or the page content. All it can do is send back some data in the response, and then it is up to your Javascript code to do something with that data.

cody_wes

Re: Re: make jquery value available in php

3 years ago

(in advance to clear out ongoing solving of the problem in the OP; I solved the initial problem in the OP)

Then I would like to ask some questions about the last posting.

It clarifies a little bit what it is. You explain that AJAX is a way to send data to and from a browser to a server without sending the whole page. (its asynchronous)

You write that PHP cannot directly change anything in the page as it has no access to the Javascript variables.

The last sentence raises much more questions. In what way should the response deliver the variable to make it available?

I want to open a new posting about this with a new example.

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