goo.gl.php

<?php
$longUrl = 'http://www.your-log-url-here.......';
$apiKey = 'Your Google Api Key here';
//You can get API key here : http://code.google.com/apis/console/

$postData = array('longUrl' => $longUrl, 'key' => $apiKey);
$jsonData = json_encode($postData);

$curlObj = curl_init();

curl_setopt($curlObj, CURLOPT_URL, 'https://www.googleapis.com/urlshortener/v1/url');

curl_setopt($curlObj, CURLOPT_RETURNTRANSFER, 1);

curl_setopt($curlObj, CURLOPT_SSL_VERIFYPEER, 0);

curl_setopt($curlObj, CURLOPT_HEADER, 0);

curl_setopt($curlObj, CURLOPT_HTTPHEADER, array('Content-type:application/json'));

curl_setopt($curlObj, CURLOPT_POST, 1);

curl_setopt($curlObj, CURLOPT_POSTFIELDS, $jsonData);

$response = curl_exec($curlObj);

$json = json_decode($response);

curl_close($curlObj);
echo 'Shortened URL ->'.$json->id;
?>