Authenticate.php

<?php

define("EVENTBRITE_OAUTH_BASE", "https://www.eventbrite.com/oauth/");

function createAuthorizeUrl($client_key)
{
	return EVENTBRITE_OAUTH_BASE . 'authorize?response_type=code&client_id=' . $client_key;
}

function handshake($code, $client_secret, $app_key)
{
	$post_args = array('code'=>$code,
		               'client_secret'=>$client_secret,
		               'client_id'=>$app_key,
		               'grant_type'=>'authorization_code');
	$data = http_build_query($post_args);

    $options = array(
        'http'=>array(
            'method'=>'POST',
            'header'=>"Content-type: application/x-www-form-urlencoded",
            'content'=>$data,
            'ignore_errors'=>true
        )
    );

    $url = EVENTBRITE_OAUTH_BASE . 'token';

    $context  = stream_context_create($options);

    $result = file_get_contents($url, false, $context);

    /* this is where we will handle errors. Eventbrite errors are a part of the response payload and are returned as an associative array. */
    return json_decode($result, true);

}