JSFiddle - React, Tailwind, and code Playground

HTML

<button id="mybutt">Show Modal</button>
<button id="yourbutt">Different Content</button>

<div id="myOverlay"></div>
<div id="myModal">
    <img src="http://placekitten.com/450/325" />
    <input type="button" id="shutme" value="Close" />
</div>
<div id="content">
    This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. This is a bunch of content. 
</div>

CSS

#content{background:wheat;}
#myOverlay{position:fixed;top:0;left:0;height:100%;width:100%;background:black;opacity:0.7;display:none;z-index:1;}
#myModal{position:fixed;top:10%;left:10%;border:3px solid darkcyan;display:none;z-index:2;}
#shutme{position:absolute;right:20px;bottom:20px;}

JavaScript

$('#mybutt').click(function(){
    $('#myOverlay').show();
    $('#myModal').show();
});
$('#yourbutt').click(function(){
    $.ajax({
        type: 'post',
        url: 'your_php_processor_file.php',
        data: 'elementID=' +myId,
        success: function(mydata){
            $('#myModal').html(mydata);
            $('#myOverlay').show();
            $('#myModal').show();
        }
    });
});

$('#shutme, #myOverlay').click(function(){
    $('#myModal').hide();
    $('#myOverlay').hide();
    $('#myModal').html('<img src="http://placekitten.com/450/325" />');
});