Getting the screen resolution using PHP

Easiest way

<?php 
//-- you can modified it like you want

echo $width = "<script>document.write(screen.width);</script>";
echo $height = "<script>document.write(screen.height);</script>";

?>

You can't do it with pure PHP. You must do it with JavaScript. There are several articles written on how to do this.

Essentially, you can set a cookie or you can even do some Ajax to send the info to a PHP script. If you use jQuery, you can do it something like this:

jquery:

$(function() {
    $.post('some_script.php', { width: screen.width, height:screen.height }, function(json) {
        if(json.outcome == 'success') {
            // do something with the knowledge possibly?
        } else {
            alert('Unable to let PHP know what the screen resolution is!');
        }
    },'json');
});

PHP (some_script.php)

<?php
// For instance, you can do something like this:
if(isset($_POST['width']) && isset($_POST['height'])) {
    $_SESSION['screen_width'] = $_POST['width'];
    $_SESSION['screen_height'] = $_POST['height'];
    echo json_encode(array('outcome'=>'success'));
} else {
    echo json_encode(array('outcome'=>'error','error'=>"Couldn't save dimension info"));
}
?>

All that is really basic but it should get you somewhere. Normally screen resolution is not what you really want though. You may be more interested in the size of the actual browser's view port since that is actually where the page is rendered...

PHP is a server side language - it's executed on the server only, and the resultant program output is sent to the client. As such, there's no "client screen" information available.

That said, you can have the client tell you what their screen resolution is via JavaScript. Write a small scriptlet to send you screen.width and screen.height - possibly via AJAX, or more likely with an initial "jump page" that finds it, then redirects to http://example.net/index.php?size=AxB

Though speaking as a user, I'd much prefer you to design a site to fluidly handle any screen resolution. I browse in different sized windows, mostly not maximized.

Directly with PHP is not possible but...

I write this simple code to save screen resolution on a PHP session to use on an image gallery.

<?php
session_start();
if(isset($_SESSION['screen_width']) AND isset($_SESSION['screen_height'])){
    echo 'User resolution: ' . $_SESSION['screen_width'] . 'x' . $_SESSION['screen_height'];
} else if(isset($_REQUEST['width']) AND isset($_REQUEST['height'])) {
    $_SESSION['screen_width'] = $_REQUEST['width'];
    $_SESSION['screen_height'] = $_REQUEST['height'];
    header('Location: ' . $_SERVER['PHP_SELF']);
} else {
    echo '<script type="text/javascript">window.location = "' . $_SERVER['PHP_SELF'] . '?width="+screen.width+"&height="+screen.height;</script>';
}
?>

New Solution If you need to send another parameter in Get Method (by Guddu Modok)

<?php
session_start();
if(isset($_SESSION['screen_width']) AND isset($_SESSION['screen_height'])){
    echo 'User resolution: ' . $_SESSION['screen_width'] . 'x' . $_SESSION['screen_height'];
    print_r($_GET);
} else if(isset($_GET['width']) AND isset($_GET['height'])) {
    $_SESSION['screen_width'] = $_GET['width'];
    $_SESSION['screen_height'] = $_GET['height'];
$x=$_SERVER["REQUEST_URI"];    
    $parsed = parse_url($x);
$query = $parsed['query'];
parse_str($query, $params);
unset($params['width']);
unset($params['height']);
$string = http_build_query($params);
$domain=$_SERVER['PHP_SELF']."?".$string;
        header('Location: ' . $domain);
} else {
$x=$_SERVER["REQUEST_URI"];    
    $parsed = parse_url($x);
$query = $parsed['query'];
parse_str($query, $params);
unset($params['width']);
unset($params['height']);
$string = http_build_query($params);
$domain=$_SERVER['PHP_SELF']."?".$string;
    echo '<script type="text/javascript">window.location = "' . $domain . '&width="+screen.width+"&height="+screen.height;</script>';
}
?>