2 JSON. Only 1 work. json_decode php - php

Question

I seriously got gray hair.
I would like to echo the [ask] data for https://api.gdax.com/products/btc-usd/ticker/
But it's return null.
When i try with to use another API with almost the same json, it work perfect.
This example works
<?php
$url = "https://api.bitfinex.com/v1/ticker/btcusd";
$json = json_decode(file_get_contents($url), true);
$ask = $json["ask"];
echo $ask;
This example return null
<?php
$url = "https://api.gdax.com/products/btc-usd/ticker/";
$json = json_decode(file_get_contents($url), true);
$ask = $json["ask"];
echo $ask;
Anybody there has an good explanation, whats wrong with the code returning null

Answer 1

the server of that null result is preventing php agent to connect thus returning http 400 error. you need to specify a user_agent value to your http request.
e.g.
$ua = 'Mozilla/5.0 (Macintosh; Intel Mac OS X 10_12_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/59.0.3071.115 Safari/537.36';
$options = array('http' => array('user_agent' => $ua));
$context = stream_context_create($options);
$url = "https://api.gdax.com/products/btc-usd/ticker/";
$json = json_decode(file_get_contents($url, false, $context), true);
$ask = $json["ask"];
echo $ask;
you can also use any user_agent string you want on the $ua variable, as long as you make sure that your target server allows it.

Answer 2

You can't access this URL without passing arguments. It happen some time when the host is checking from where the request come.
$ch = curl_init();
$header=array('GET products/btc-usd/ticker/ HTTP/1.1',
'Host: api.gdax.com',
'Accept:text/html,application/xhtml+xml,application/xml;q=0.9,*/*;q=0.8',
'Accept-Language:en-US,en;q=0.8',
'Cache-Control:max-age=0',
'Connection:keep-alive',
'Host:adfoc.us',
'User-Agent:Mozilla/5.0 (Macintosh; Intel Mac OS X 10_8_4) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/27.0.1453.116 Safari/537.36',
);
curl_setopt($ch,CURLOPT_URL,"https://api.gdax.com/products/btc-usd/ticker/");
curl_setopt($ch,CURLOPT_RETURNTRANSFER,true);
curl_setopt($ch,CURLOPT_CONNECTTIMEOUT,0);
curl_setopt($ch,CURLOPT_HTTPHEADER,$header);
$result=curl_exec($ch);
Then you can use json_decode() on $result !