Googleの短縮URL「goo.gl」がAPIの提供を開始http://blog.fkoji.com/2011/01110730.html
したらしいので早速いじってみました。
 

 
あらかじめ下記サイトでAPIキーを取得しておきましょう。
URL Shortener APIのActivateボタンを押して表示されたURLのkeyの値がAPIキーです。
http://code.google.com/apis/console/
APIキーを取得したらあとはごりごり書くだけ。
 
PHP

< ?php
$apikey='APIキー';
$url="https://www.googleapis.com/urlshortener/v1/url" . '?key=' . $apikey;
$longurl=$_GET["longUrl"];
$shorturl=$_GET["shortUrl"];

if($longurl){
	$request='{"longUrl": "' . $longurl . '"}';
	$headers = array('Content-Type:application/json');
	$conn = curl_init();
	curl_setopt($conn, CURLOPT_URL, $url);
	curl_setopt($conn, CURLOPT_SSL_VERIFYPEER, false);
	curl_setopt($conn, CURLOPT_POSTFIELDS, $request);
	curl_setopt($conn, CURLOPT_RETURNTRANSFER, 1);
	curl_setopt($conn, CURLOPT_POST, true);
	curl_setopt($conn, CURLOPT_HEADER, false);
	curl_setopt($conn, CURLOPT_HTTPHEADER, $headers);
}elseif($shorturl){
	$url .= '&shortUrl=' . $shorturl;
	$conn = curl_init();
	curl_setopt($conn, CURLOPT_URL, $url);
	curl_setopt($conn, CURLOPT_SSL_VERIFYPEER, false);
	curl_setopt($conn, CURLOPT_RETURNTRANSFER, 1);
	curl_setopt($conn, CURLOPT_HEADER, false);
}else{
	echo "error";
	exit;
}
$ret=curl_exec($conn);
echo $ret;
curl_close($conn);
exit;
?>

 
Javascript

//短縮するとき
var m={'longUrl':対象URL};
ajax_get('action.php', m, when_get_shorturl);

//元に戻すとき
var m={'shortUrl':対象URL};
ajax_get('action.php', m, when_get_longurl);

function when_get_shorturl(data){
	var m=eval("("+data+")");
}

function when_get_longurl(data){
	var m=eval("("+data+")");
}

function ajax_get(cgi_path, param, finish_func){
	var httpObj = createHttpRequest();
	if(!httpObj)return;
	var str=get_post_param(param);
	if(str!="")cgi_path+=('?'+str);
	httpObj.open("GET",cgi_path, true);
	httpObj.onreadystatechange=function(){
		if(httpObj.readyState == 4 && httpObj.status == 200){
			var data=httpObj.responseText;
			finish_func(data);
		}
	}
	httpObj.setRequestHeader('Content-Type','application/x-www-form-urlencoded; charset=UTF-8');
	httpObj.send();
}

function get_post_param(param){
	if(!param)return "";
	var a;
	var str="";
	var m;
	var b;
	for(b in param){
		str+=b+"="+encodeURIComponent(param[b]);
		str+="&";
	}
	str=str.substring(0,str.length-1);
	return str;
}
function createHttpRequest(){
    var x=null;
    if (window.XMLHttpRequest)return new XMLHttpRequest();
    try {
        return new ActiveXObject("Msxml2.XMLHTTP");
    } catch(e) {
        try {
            return new ActiveXObject("Microsoft.XMLHTTP");
        } catch(e) {
            x = null;
        }
    }
    return x;
}

 

参考にしたサイト
 
Google Code – Google URL Shortener API
http://code.google.com/intl/ja/apis/urlshortener/