$json = file_get_contents('url_here');
$obj = json_decode($json);
echo $obj->access_token;

For this to work, file_get_contents requires that allow_url_fopen is enabled. This can be done at runtime by including:

ini_set("allow_url_fopen", 1);

You can also use curl to get the URL. To use curl, you can use the example found here:

$ch = curl_init();
// IMPORTANT: the below line is a security risk, read https://paragonie.com/blog/2017/10/certainty-automated-cacert-pem-management-for-php-software
// in most cases, you should set it to true
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_URL, 'url_here');
$result = curl_exec($ch);
curl_close(obj = json_decode($result);
echo $obj->access_token;

What you need is a request php page, which will make:

1 - Get data from the site:

$data = file_get_contents('https://blockchain.info/ticker');

2 - decode the json

$decodedData = json_decode($data);

3 - Here you can access it using OOP:

var_dump($decodedData->USD);

The point here will be to retrieve data as you wish, you can mix it up with HTML in a table for example.

Then, you need a JS script, that will execute a function with setInterval, each few miliseconds. That function should make a request to a PHP page that you created earlier, get that data and change with the updated one.

json_decode() expects a string, not a URL. You're trying to decode that url (and json_decode() will NOT do an http request to fetch the url's contents for you).

You have to fetch the json data yourself:

$json = file_get_contents('http://...'); // this WILL do an http request for you
$data = json_decode($json);
echo $data->{'token'};

You can do something like that :

<?php 
$json_url = "http://www.myapifilms.com/imdb/top";
$json = file_get_contents($json_url);
$data = json_decode($json, TRUE);
echo "<pre>";
print_r($data);
echo "</pre>";
?>

You are incorrectly addressing the data in the PHP object created from the JSON String

$json = file_get_contents('https://...link/here..');
$obj = json_decode($json);
echo $obj->data[0]->Position;

Or if there are more occurances

foreach ( $obj->data as $idx=>$data) {
    echo $data->Position;
}