php

/** javascript **/
(function () {
	"use strict";
    if (document.cookie.indexOf('device_pixel_ratio') === -1 && 'devicePixelRatio' in window && window.devicePixelRatio === 2) {
        var date = new Date();
        date.setTime(date.getTime() + 3600000);
        document.cookie = 'device_pixel_ratio=' + window.devicePixelRatio + ';' + ' expires=' + date.toUTCString() + '; path=/';

        if (document.cookie.indexOf('device_pixel_ratio') !== -1) {
            window.location.reload();
        }
    }
})();

/** php **/

/**
 * Detect retina device
 */
function jeg_is_retina_device()
{
	if(isset($_COOKIE["device_pixel_ratio"])) {
		return $_COOKIE["device_pixel_ratio"] > 1;
	} else {
		return false;
	}
}