Invalid argument supplied for foreach() - Bing Sea

This is the php code:

<?php

$acctKey = 'key';

$rootUri = 'https://api.datamarket.azure.com/Bing/Search';

$contents = file_get_contents('bing_basic.html');

if ($_POST['query'])
{

$query = urlencode("'{$_POST['query']}'");

$serviceOp = $_POST['service_op'];

$requestUri = "$rootUri/$serviceOp?\$format=json&Query=$query";

$auth = base64_encode("$acctKey:$acctKey");

$data = array('http' => array('request_fulluri' => true,'ignore_errors' => true,'header' => "Authorization: Basic $auth"));

$context = stream_context_create($data);

$response = file_get_contents($requestUri, 0, $context);

$jsonObj = json_decode($response);
$resultStr = '';
foreach($jsonObj->d->results as $value)
{
    switch ($value->__metadata->type)
    {
        case 'WebResult':
        $resultStr .= "<a href=\"{$value->Url}\">{$value->Title}</a><p>{$value->Description}</p>";
        break;
        case 'ImageResult': $resultStr .= "<h4>{$value->Title} ({$value->Width}x{$value->Height}) " . "{$value->FileSize} bytes)</h4>" . "<a href=\"{$value->MediaUrl}\">" . "<img src=\"{$value->Thumbnail->MediaUrl}\"></a><br />";
        break;
    }
}

$contents = str_replace('{RESULTS}', $resultStr, $contents);

}

echo $contents;

?>

And tis is the html:

<html>
<head>
<title>Bing Search Tester (Basic)</title>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
</head>
<body>
<h1>Bing Search Tester (Basic)</h1>
<form method="POST" action="bing_basic.php">
<label for="service_op">Service Operation</label><br/>
<input name="service_op" type="radio" value="Web" CHECKED /> Web
<input name="service_op" type="radio" value="Image" /> Image <br/>
<label for="query">Query</label><br/>
<input name="query" type="text" size="60" maxlength="60" value="" /><br /><br />
<input name="bt_search" type="submit" value="Search" />
</form> <h2>Results</h2>
{RESULTS} 
</body>
</html>

Why do I keep getting that error ? This is a duplicate by the way, but the other questions didn't have all the code and there were no answers to my question.

Also, I'm not very familiar with php objects and json..

Api documentation: https://onedrive.live.com/view.aspx?resid=9C9479871FBFA822!112&app=Word&authkey=!ANNnJQREB0kDC04

Double check to ensure that $jsonObj->d->results is indeed an array or that its not empty.

if( ( is_array( $jsonObj->d->results ) && ( ! empty( $jsonObj->d->results ) ) {
    foreach($jsonObj->d->results as $value)
    {
        switch ($value->__metadata->type)
        {
            case 'WebResult':
            $resultStr .= "<a href=\"{$value->Url}\">{$value->Title}</a><p>{$value->Description}</p>";
            break;
            case 'ImageResult': $resultStr .= "<h4>{$value->Title} ({$value->Width}x{$value->Height}) " . "{$value->FileSize} bytes)</h4>" . "<a href=\"{$value->MediaUrl}\">" . "<img src=\"{$value->Thumbnail->MediaUrl}\"></a><br />";
            break;
        }
    }
} else {
    if( ! is_array( $jsonObj->d->results ) {
        echo "jsonObj->d->results is not an array!";
    } elseif( empty( $jsonObj->d->results ) {
        echo "jsonObj->d->results is empty!";
    }
}