Example of code to obtain an Access Token

$client_id = '';
$client_secret = '';
$endpoint = "http://site.dev";

$curl = curl_init($endpoint . '/oauth2/token');

curl_setopt($curl, CURLOPT_RETURNTRANSFER, true);
curl_setopt($curl, CURLOPT_POST, true);
curl_setopt($curl, CURLOPT_HEADER,'Content-Type: application/x-www-form-urlencoded');
curl_setopt($curl, CURLOPT_SSL_VERIFYPEER, false);

$params = array(
  "client_id" => $client_id,
  "client_secret" => $client_secret,
  "grant_type" => "client_credentials",
);

$postData = "";

foreach($params as $k => $v)  {
  $postData .= $k . '='.urlencode($v).'&';
}

$postData = rtrim($postData, '&');
curl_setopt($curl, CURLOPT_POSTFIELDS, $postData);

$json_response = curl_exec($curl);
$status = curl_getinfo($curl, CURLINFO_HTTP_CODE);

if ($status != 200) {
  print curl_error($curl);
}

curl_close($curl);

print $json_response;