REST API：Fat Secret API无效签名：PHP中的oauth_signature

Question

I am using Fat Secret API in my project and want to find the food names on search so I hard coded the food name say : banana and it is giving me error

8 Invalid signature: oauth_signature 'NECnoAOp6D2qLCg7YQ84fYyJYRE='

Below is my code

$consumer_key = "bcd69xxxxxxxxxxxxxxxxxxxxxxx52";
$secret_key = "62fe9xxxxxxxxxxxxxxxxxxxxxxxx54d";

$base = rawurlencode("GET")."&";
    $base .= "http%3A%2F%2Fplatform.fatsecret.com%2Frest%2Fserver.api&";
    $params = "format=json&";
    $params = "method=foods.search&";
    $params .= "oauth_consumer_key=$consumer_key&";
    $params .= "oauth_nonce=".uniqid()."&";
    $params .= "oauth_signature_method=HMAC-SHA1&";
    $params .= "oauth_timestamp=".time()."&";
    $params .= "oauth_version=1.0&";
    $params .= "search_expression=banana";
    $params .= "oauth_callback=oob";
    $params2 = rawurlencode($params);
    $base .= $params2;

//encrypt it!
$sig= base64_encode(hash_hmac('sha1', $base, "62fe9d66898545a0b48d497a4394054d&", true));
    $url = "http://platform.fatsecret.com/rest/server.api?".$params."&oauth_signature=".rawurlencode($sig);
//$food_feed = file_get_contents($url);
list($output,$error,$info) = loadFoods($url);
echo '<pre>';
if($error == 0){
    if($info['http_code'] == '200'){
        echo $output;
        } else {
       die('Status INFO : '.$info['http_code']);
}
}else{
 die('Status ERROR : '.$error);
}
function loadFoods($url)
{

        // create curl resource
        $ch = curl_init();

        // set url
        curl_setopt($ch, CURLOPT_URL, $url);

        //return the transfer as a string
        curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);

        // $output contains the output string
        $output = curl_exec($ch);

        $error = curl_error($ch);

        $info = curl_getinfo($ch);
        // close curl resource to free up system resources
        curl_close($ch);

        return array($output,$error,$info);

}

Please Help me in this. I am new in OAuth and Fat Secret API, Please do share the necessary information if you know.

Thanks