This code uses Zend Framework’s Zend_Json::decode method, however you can use json_decode if it is available on your version of PHP.

Create the authorization link
When this link is clicked, the site visitor is presented with a page from Google asking if they would like to allow your application access to their data. If they accept, Google will give them a code, which can then be used on the next request. This is run as an installed application, because there are times when data will be requested without user interaction.

$sAuthURL=AUTH_URL;
$aParms=array('response_type'=>RESPONSE_TYPE,
        'client_id'=>CLIENT_ID,
        'redirect_uri'=>REDIRECT_URI,
        'scope'=>SCOPE);
$sLink=$sAuthURL.'?'.http_build_query($aParms);

Request an access and refresh token

        require_once 'Zend/Json.php';
        $sTokenURL=TOKEN_URL;
        $aParms=array(
                'code'=>$_POST['code'],
                'client_id'=>CLIENT_ID,
                'client_secret'=>CLIENT_SECRET,
                'redirect_uri'=>REDIRECT_URI,
                'grant_type'=>AUTHORIZATION_CODE);
        $cURL=curl_init();
        curl_setopt($cURL,CURLOPT_URL,$sTokenURL);
        curl_setopt($cURL,CURLOPT_SSL_VERIFYPEER,TRUE);
        curl_setopt($cURL,CURLOPT_POST, TRUE);
        curl_setopt($cURL,CURLOPT_RETURNTRANSFER, TRUE);
        curl_setopt($cURL,CURLOPT_POSTFIELDS,$aParms);
        $cResponse=Zend_Json::decode(trim(curl_exec($cURL)));
        curl_close($cURL);                
        $sAccessToken=$cResponse['access_token'];
        $sRefreshToken=$cResponse['refresh_token'];

Use the refresh_token to request a new access_token

                                $sTokenURL=TOKEN_URL;
                                $aParms=array(
                                        'refresh_token'=>$sRefreshToken,
                                        'client_id'=>CLIENT_ID,
                                        'client_secret'=>CLIENT_SECRET,
                                        'grant_type'=>REFRESH_TOKEN);
                                $cURL=curl_init();
                                curl_setopt($cURL,CURLOPT_URL,$sTokenURL);
                                curl_setopt($cURL,CURLOPT_SSL_VERIFYPEER,TRUE);
                                curl_setopt($cURL,CURLOPT_POST, TRUE);
                                curl_setopt($cURL,CURLOPT_RETURNTRANSFER, TRUE);
                                curl_setopt($cURL,CURLOPT_POSTFIELDS,$aParms);
                                require_once 'Zend/Json.php';
                                $cResponse=Zend_Json::decode(trim(curl_exec($cURL)));
                                $sError=curl_error($cURL);
                                curl_close($cURL);
                                $sAccessToken=$cResponse['access_token'];

Request the contact data

                $sContactsURL=CONTACTS_URL.'?access_token='.$sAccessToken;
                $cURL=curl_init();
                curl_setopt($cURL,CURLOPT_URL,$sContactsURL);
                curl_setopt($cURL,CURLOPT_RETURNTRANSFER, TRUE);
                $cResponse=trim(curl_exec($cURL));
                $sError=curl_error($cURL);
                curl_close($cURL);

Parse the data from Google
This code also Zend_Gdata to handle the parsing.

$phone_only=false;

include 'Zend/Gdata.php';

$gdata=new Zend_Gdata();
$feed=$gdata->importString($cResponse);

foreach ($feed as $entry) {
        // Thanks to: http://www.ibm.com/developerworks/opensource/library/x-phpgooglecontact/index.html
        $xml = simplexml_load_string($entry->getXML());
        $obj = new stdClass;
        $obj->id = $entry->id->text;
        if (false===($iSlash=strpos($entry->title->text,'/')))
                $obj->name=$entry->title->text;
        else
                $obj->name = substr($entry->title->text,0,$iSlash);
        if (empty($obj->name)) continue;
        $name = explode(' ',$obj->name,3);
        $obj->first_name = $obj->middle_name = $obj->last_name = '';
        switch (count($name))
        {
                case 1: 
                        $obj->first_name = $obj->name;
                        break;
                case 2: 
                        $obj->first_name = $name[0];
                        $obj->last_name = $name[1];
                        break;
                case 3:
                        $obj->first_name = $name[0];
                        $obj->middle_name = $name[1];
                        $obj->last_name = $name[2];
                        break;
        }
        $obj->phoneNumber = array();
        $obj->phone = array();
        foreach ($xml->phoneNumber as $p) 
        {
                $type = preg_replace('/^[^#]+#(.*)$/','\1',(string) $p['rel']);
                $obj->phoneNumber[] = (string) $p.' ('.$type.')';
                $obj->phone[$type] = array ('phone' => preg_replace('/\D/','',(string) $p), 'type' => strtolower($type) );
        }
        if (empty($obj->phone) && $phone_only) continue;
        $results[$obj->last_name] = $obj;  
}
ksort($results);

This post courtesy of Lyrix, Inc. http://mobiso.com