Analytics Data Export API使用PHP脚本错误

I am using a php script to export data from Adobe Analytics. I choose the dimensions (elements) and the metrics and it works. Now, I am trying to add the granularity in my code and I am getting an error.

<?php
include_once('/path/SimpleRestClient.php');

// Date 
$date = date("Y-m-d",strtotime("-1 days"));

function GetAPIData($method, $data) 
{
    $username       = "XXXXX"; 
    $shared_secret  = "XXXXX";
    $postURL        = "https://api3.omniture.com/admin/1.4/rest/?method=";  

    // Nonce is a simple unique id to each call to prevent MITM attacks.
    $nonce      = md5(uniqid(php_uname('n'), true));
    // The current timestamp in ISO-8601 format
    $nonce_ts   = date('c');
    /* The Password digest is a concatenation of the nonce, it is timestamp and your password 
    (from the same location as your username) which runs through SHA1 and then through a base64 encoding */
    $digest     = base64_encode(sha1($nonce . $nonce_ts . $shared_secret));

    $rc = new SimpleRestClient();    
    $rc -> setOption(CURLOPT_HTTPHEADER, array("X-WSSE: UsernameToken Username=\"$username\", PasswordDigest=\"$digest\", Nonce=\"$nonce\", Created=\"$nonce_ts\""));
    //var_dump($o);

    $rc -> postWebRequest($postURL .$method, $data);    
    return $rc;
}

$method = 'Report.Queue'; 
$data       ='
            {
                "reportDescription":
                {
                "reportSuiteID":"XXXXX",
                "date":"'.$date.'",
                "dateGranularity":"day",
                "elements":[{"id":"lasttouchchannel"}],
                "metrics":[{"id":"visits"},{"id":"instances"},{"id":"event7"}]                
                }
            }';

$rc=GetAPIData($method, $data);


if($rc -> getStatusCode() == 200) // status code 200 is for 'ok'
{
    $counter    = 0; 
    do
    {
        if($counter>0){sleep($sleep = 120);}
        $return = GetAPIData('Report.Get', $rc->getWebResponse());
        $counter++;
    }while($return -> getStatusCode() == 400 && json_decode($return->getWebResponse())->error == 'report_not_ready'); // status code 400 is for 'bad request'

    // 
    $json=json_decode($return->getWebResponse());

    foreach ($json->report->data as $el) 
    {
        echo $el->name.": ".$el->counts[0].": ".$el->counts[1].": ".$el->counts[2]."
";

        // Adding the data in the CSV file without overwriting the previous data
        //array_push($list, array($el->name, $el->counts[0], ($el->counts[1])/($el->counts[2])));
    }   

}
else
{
    echo "Wrong";
}
/*  
$fp = fopen($adobe_file, 'w');

foreach ($list as $fields) 
{
    // Save the data into a CSV file
    fputcsv($fp, $fields);
}

fclose($fp);
*/
?>

Without this line "dateGranularity":"day", the code works. With this line I am getting the error:

Undefined property: stdClass::$counts