使用PHP和/或JavaScript的iPhone4视网膜显示检测

<?php
    $imgPath = \"images/\";
    if(isset($_COOKIE[\"imgRes\"])){
        $imgRes = $_COOKIE[\"imgRes\"];
        if( $imgRes  >= 2 ){
            $imgPath = \"images/highRes/\";
        }
    } else {
?>
    <script language=\"javascript\">
        var the_cookie = \"imgRes=\"+window.devicePixelRatio+\";\"+the_cookie;
        document.cookie = the_cookie;
        location = \'<?=$_SERVER[\'PHP_SELF\']?>\';
    </script>
<?php
    }
?>

var retina = window.devicePixelRatio && window.devicePixelRatio >= 2;

var retina = window.devicePixelRatio > 1 ? true : false;