The problem for that particular URL is that it's expecting a different User Agent, different to the default that PHP is using with file_get_contents()
Here is a better example using CURL. It's more robust although it takes more lines of code to configure it and make it run:
// create curl resource
$ch = curl_init();
// set the URL
curl_setopt($ch, CURLOPT_URL, 'https://erikberg.com/nba/standings.json');
// Return the transfer as a string
curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1);
// Fake the User Agent for this particular API endpoint
curl_setopt($ch, CURLOPT_USERAGENT, 'Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.8.1.13) Gecko/20080311 Firefox/2.0.0.13');
// $output contains the output string.
$output = curl_exec($ch);
// close curl resource to free up system resources.
curl_close($ch);
// You have your JSON response here
echo $output;