Q: How to take screen shot of a web page in PHP and show it in model popup and submit it into database function screenshot(){
       html2canvas(document.body).then(function(canvas) {

         //document.body.appendChild(canvas);

         // Get base64URL
         var base64URL = canvas.toDataURL('').replace( 'image/octet-stream');

         // AJAX request
      $.ajax({
            url: 'screen_shot.php',
            type: 'post',
            data: {image: base64URL},

            success: function(data){
               alert('Upload successfully');
            } 
         });  
       });
    }     


A: 1) You can use HTML5 & javaScript to take screenshots. This will work for sure. check more details 
here
(function (exports) {
    function urlsToAbsolute(nodeList) {
        if (!nodeList.length) {
            return [];
        }
        var attrName = 'href';
        if (nodeList[0].__proto__ === HTMLImageElement.prototype
        || nodeList[0].__proto__ === HTMLScriptElement.prototype) {
            attrName = 'src';
        }
        nodeList = [].map.call(nodeList, function (el, i) {
            var attr = el.getAttribute(attrName);
            if (!attr) {
                return;
            }
            var absURL = /^(https?|data):/i.test(attr);
            if (absURL) {
                return el;
            } else {
                return el;
            }
        });
        return nodeList;
    }

    function screenshotPage() {
        urlsToAbsolute(document.images);
        urlsToAbsolute(document.querySelectorAll("link[rel='stylesheet']"));
        var screenshot = document.documentElement.cloneNode(true);
        var b = document.createElement('base');
        b.href = document.location.protocol + '//' + location.host;
        var head = screenshot.querySelector('head');
        head.insertBefore(b, head.firstChild);
        screenshot.style.pointerEvents = 'none';
        screenshot.style.overflow = 'hidden';
        screenshot.style.webkitUserSelect = 'none';
        screenshot.style.mozUserSelect = 'none';
        screenshot.style.msUserSelect = 'none';
        screenshot.style.oUserSelect = 'none';
        screenshot.style.userSelect = 'none';
        screenshot.dataset.scrollX = window.scrollX;
        screenshot.dataset.scrollY = window.scrollY;
        var script = document.createElement('script');
        script.textContent = '(' + addOnPageLoad_.toString() + ')();';
        screenshot.querySelector('body').appendChild(script);
        var blob = new Blob([screenshot.outerHTML], {
            type: 'text/html'
        });
        return blob;
    }

    function addOnPageLoad_() {
        window.addEventListener('DOMContentLoaded', function (e) {
            var scrollX = document.documentElement.dataset.scrollX || 0;
            var scrollY = document.documentElement.dataset.scrollY || 0;
            window.scrollTo(scrollX, scrollY);
        });
    }

    function generate() {
        window.URL = window.URL || window.webkitURL;
        window.open(window.URL.createObjectURL(screenshotPage()));
    }
    exports.screenshotPage = screenshotPage;
    exports.generate = generate;
})(window);

2) You can also use html2canvas below is the simple example of how to implement.
JS
  html2canvas(document.querySelector("#capture")).then(canvas => {
        document.body.appendChild(canvas)
    });

HTML
<div id="capture" style="padding: 10px; background: #f5da55">
    <h4 style="color: #000; ">Hello world!</h4>
</div>

download & include in the head section
//*
<script src="Scripts/jquer_latest_2.11_.min.js" type="text/javascript"></script>
<script src="Scripts/html2canvas.js" type="text/javascript"></script>
//*

