I want to make a responsive banner, that changes depending of the resolution screen with php, js and html

Question

I confess that I have a poor knowledge in php and js, but I'm trying to innovate and make a descent website. So I made 2 different slides, one for desktop and one for mobile, got a shortcode and i'm trying to put that in a html widget using a js screen width detection and mentioning it in the php code. Maybe its wrong in lots of levels but as I said I have no knowledge about that, so obviously didn't work and the code just gave me a blank widget. What am I doing wrong?

    <script type="text/javascript">
$(document).ready(function () {
  createCookie("width", $(window).width());
});
</script>

<?php
if ($_COOKIE["height"] => 768px) {
    echo do_shortcode('[URIS id=2822]');
} 
    else {
        echo do_shortcode('[URIS id=2883]');
    }

?>

The error message is:

768px) { echo do_shortcode('[URIS id=2822]'); } else { echo do_shortcode('[URIS id=2883]'); } ?>

Answer 1

My friend @ChristophKern helped me and I realize it was simpler than I though, I just used html and css instead js and php. The full code is:

<style>
@media only screen and (min-width: 768px) 
{
  #slider-pro-3-2883 
   {
    display: none;
   }
}

@media only screen and (max-width: 767px) 
{
  #slider-pro-3-2822 
   {
    display: none !important;
   }
}
</style>

[URIS id=2822]
[URIS id=2883]

Thank you Chris and Funk Forty Niner for the time spend to help me <3