いいねボタンを非同期読み込みでスピードアップする

gistfile1.txt

<!-- Facebook Scripts -->
<div id="fb-root"></div>

<script type="text/javascript">// <![CDATA[
  window.fbAsyncInit = function() {
    FB.init({
      appId      : 'アプリIDをここに書く', // ENTER your FB App ID
      channelUrl : 'http://daipresents.com/channel.php', // Channel File
      status     : true, // check login status
      cookie     : true, // enable cookies to allow the server to access the session
      xfbml      : true  // parse XFBML
    });

    // いいねのトラッキング用
    _ga.trackFacebook(); //Google Analytics tracking

  };

  // Load the SDK's source Asynchronously
  (function(d, debug){
     var js, id = 'facebook-jssdk', ref = d.getElementsByTagName('script')[0];
     if (d.getElementById(id)) {return;}
     js = d.createElement('script'); js.id = id; js.async = true;
     js.src = "//connect.facebook.net/ja_JP/all" + (debug ? "/debug" : "") + ".js";
     ref.parentNode.insertBefore(js, ref);
   }(document, /*debug*/ false));
// ]]></script>

gistfile2.txt

<?php
  $cache_expire = 60*60*24*365;
  header("Pragma: public");
  header("Cache-Control: max-age=".$cache_expire);
  header('Expires: ' . gmdate('D, d M Y H:i:s', time()+$cache_expire) . ' GMT');
?>
<script type="text/javascrip" src="/connect.facebook.net/ja_JP/all.js"></script>