<?
$ch = curl_init();
$url = 'https://opendata.nationalrail.co.uk/authenticate';

$un =  'djr931006@ymail.com';
$pw = 'Longbow1!';

$postdata = "username=" . urlencode($un);
$postdata .= "&password=" . urlencode($pw);

unset($un);
unset($pw);

//curl_setopt($ch, CURLOPT_POST, 2);
//curl_setopt($ch, CURLOPT_POSTFIELDS, json_encode($post));
//curl_setopt($ch, CURLOPT_HTTPHEADER, array('Content-Type: application/x-www-form-urlencoded'));
//curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);

curl_setopt_array($ch,
  array(
     CURLOPT_URL => $url,
     CURLOPT_HTTPHEADER =>  array('Content-Type: application/x-www-form-urlencoded'),
     // Enable the post response.
    CURLOPT_POST       => true,
    // The data to transfer with the response.
    CURLOPT_POSTFIELDS => $postdata,
    CURLOPT_RETURNTRANSFER     => true,
  )
);

// execute!
$response = curl_exec($ch);

unset($postdata);

// close the connection, release resources used
curl_close($ch);

// do anything you want with your response
$response_array = json_decode($response, true);
$token = $response_array['token'];
var_dump($token);
unset($token);
unset($reponse_array);
?>