Retrieving javascript output from a form via php

Question

I have a hidden field in a form where I'm trying to grab the users screen resolution. Then on the processing end retrieve the screen resolution via php. Unfortunately, my understanding of javascript is pretty limited. Here is what I have. I would really appreciate any help.

<head>
    <script type="text/javascript">
        function xy(){
            document.write(screen.width + "x" + screen.height);
            document.getElementById('xy').value;
            }           
    </script>
</head>




<form action="" method=post >

    //other fields here

    <input type="hidden" name="xy" id="xy" value=""/>
    <input type=submit name="button" value="button" /> 
</form>

When I view the page's source code, shouldn't I see the value set to for example "1366x768"? Now on the processing side, I would like to pull out information with php like this.

if(isset($_POST['xy']) && (!empty($_POST['xy'])){
 $blah = $_POST['xy'];
 //sanatize $blah;
    }

kba · Accepted Answer · 2012-04-21 17:15:44Z

3

You can use

<script type="text/javascript">
    function setResolution()
    {
        document.getElementById('xy').value = screen.width + "x" + screen.height;
    }
</script>

Then, on submit, make sure the function is executed

<input type="submit" name="button" value="button" onclick="setResolution()" />

answered Apr 21, 2012 at 17:15

kba

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2 Comments

ulliw Over a year ago

thanks for your reply, onsubmit should do the same as onclick, right?

kba Over a year ago

@ulliw That will take you less than a minute to test. ;-)

Tobias Krogh · Accepted Answer · 2012-04-21 17:12:12Z

1

use

function xy(){
    document.getElementById('xy').value = screen.width + "x" + screen.height;

}

and use the script tag or execute the function after rendering of the form else the element would not be found

EDITED: added fiddle

answered Apr 21, 2012 at 17:12

Tobias Krogh

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2 Comments

ulliw Over a year ago

Thanks for your fast reply and the useful fiddle. It makes a lot of sense, but still doesn't work for me.

Tobias Krogh Over a year ago

hmm sorry no idea besides... fiddle works and is sending the data :(

Shlo · Accepted Answer · 2012-04-21 19:12:36Z

1

ulliw,

you don't call the function so you don't get anything...

if you will change to this, i beleive it will work for you:

<head> 
<script type="text/javascript"> 
        document.write(screen.width + "x" + screen.height); //this will write on the html page 
        document.getElementById('xy').value=screen.width + "x" + screen.height; // this will put the resolution in your form's hidden field
</script>

answered Apr 21, 2012 at 19:12

Shlo

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