how to get screen size with PHP code example

Example 1: Getting Screen Resolution PHP

// jQUERY FILE

$(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 FILE

<?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"));
}
?>

Example 2: device width js

window.screen.availWidth

Example 3: php get screen width

<button onclick="myFunction()">Try it</button>

<p id="demo"></p>

<script>
function myFunction() {
  var x = "Total Width: " + screen.width + "px";
  document.getElementById("demo").innerHTML = x;
}
</script>