Q:

How to get past login screen on Guzzle call

I have to send information to an external website using cURL. I set up Guzzle on my Laravel application. I have the basics set up, but according to the documentation of the website, there is an action that's required for the username and password. How can I pass the 'action' along with the credentials needed to log in and get access?
The website states: 
curl [-k] –dump-header <header_file> -F “action=login” -F “username=<username>” -F “password=<password>” https://<website_URL>
My controller:
    $client = new \GuzzleHttp\Client();

    $response = $client->get('http://website.com/page/login/', array(
        'auth' => array('username', 'password')
    ));

    $xml = $response;
    echo $xml;

The website will load on the echo, but it will only pull up the login screen. I need those credentials to bypass the login screen (with a successful login) to get to the portion of information I need for cURL.

A:

curl -F submits a POST request instead of a GET request. So you'll need to modify your code accordingly, something like
$client = new \GuzzleHttp\Client();

$response = $client->post('http://website.com/page/login/', [
    'body' => [
        'username' => $username,
        'password' => $password,
        'action' => 'login'
    ],
    'cookies' => true
]
);

$xml = $response;
echo $xml;

See http://guzzle.readthedocs.org/en/latest/quickstart.html#post-requests, http://curl.haxx.se/docs/manpage.html#-F
Edit:
Just add ['cookies' => true] to requests in order to use the auth cookie associated with this GuzzleHttp\Client(). http://guzzle.readthedocs.org/en/latest/clients.html#cookies
$response2 = $client->get('http://website.com/otherpage/', ['cookies' => true]);

A:

I was having trouble getting @JeremiahWinsley's answer to work on newer version of Guzzle so I've updated their code to work as of Guzzle 5.x.
Three major changes are required

Using form_params instead of body to prevent the error "Passing in the "body" request option as an array to send a POST request has been deprecated."
Changing the cookies to use the CookieJar object
Use ->getBody()->getContents() to get the body of the request

Here is the updated code:
$client = new \GuzzleHttp\Client();
$cookieJar = new \GuzzleHttp\Cookie\CookieJar();

$response = $client->post('http://website.com/page/login/', [
    'form_params' => [
        'username' => $username,
        'password' => $password,
        'action' => 'login'
    ],
    'cookies' => $cookieJar
]
);

$xml = $response->getBody()->getContents();
echo $xml;

And to continue using cookies in future requests, pass in the cookieJar to the request:
$response2 = $client->get('http://website.com/otherpage/', ['cookies' => $cookieJar]);

A:

I was having trouble getting @JeremiahWinsley's and @Samsquanch's answer to work on newer version of Guzzle. So I've updated the code to work as of Guzzle 6.x.
Guzzle 6.x. documents: http://docs.guzzlephp.org/en/stable/index.html
Here is the updated code:
use GuzzleHttp\Client;
use GuzzleHttp\Cookie\CookieJar;

try {
        $client = new Client();
        $cookieJar = new CookieJar();

        $response = $client->request('POST', 'http://website.com/page/login/', [
            'form_params' => [
                'username' => 'test@example.com',
                'password' => '123456'
            ],
            'cookies' => $cookieJar
        ]);

        $response2 = $client->request('GET', 'http://website.com/otherpage/', [
            'cookies' => $cookieJar
        ]);

        if ($response2->getStatusCode() == 200) {
            return $response2->getBody()->getContents();
        } else {
            return "Oops!";
        }
    } catch (\Exception $exception) {
        return 'Caught exception: ', $exception->getMessage();
    }

