Get iCould contacts in PHP; this is just a very quick proof of concept (no error handling, vcard parsing, etc.)

contacts.php

<?php

/**
* 
* Only dependency required is "guzzlehttp/guzzle": "~6.0"
*
*/
include 'vendor/autoload.php';

$username = '*****@****.com';
$password = '******';

function authenticate($username, $password)
{
    $client = new \GuzzleHttp\Client();
    $response = $client->post('https://setup.icloud.com/setup/authenticate/' . $username, [
        \GuzzleHttp\RequestOptions::AUTH => func_get_args(),
        \GuzzleHttp\RequestOptions::HEADERS => [
            'Content-Type' => 'application/xml'
        ]
    ]);

    if ($response->getStatusCode() !== 200) {
        throw new Exception('Unable to login with provided credentials...');
    }

    $body = json_decode(json_encode(simplexml_load_string($response->getBody()->getContents())), true);

    $dsid = $body['dict']['dict'][0]['string'];
    $token = $body['dict']['dict'][1]['string'];

    return [$dsid, $token];
}

function getLinks($dsid, $token)
{
    $data = <<<XML
<?xml version="1.0" encoding="UTF-8"?>
<A:propfind xmlns:A="DAV:">
  <A:prop>
    <A:getetag/>
  </A:prop>
</A:propfind>
XML;
    
    $client = new \GuzzleHttp\Client();
    $response = $client->request('PROPFIND', 'https://p04-contacts.icloud.com/' . $dsid . '/carddavhome/card', [
        \GuzzleHttp\RequestOptions::HEADERS => [
            'Depth' => '1',
            'Content-Type' => 'text/xml',
            'Authorization' => 'X-MobileMe-AuthToken ' . base64_encode(sprintf('%s:%s', $dsid, $token)),
        ],
        \GuzzleHttp\RequestOptions::BODY => $data
    ]);

    $body = json_decode(json_encode(simplexml_load_string($response->getBody()->getContents())), true);

    $output = <<<XML
<?xml version="1.0" encoding="UTF-8"?>
<F:addressbook-multiget xmlns:F="urn:ietf:params:xml:ns:carddav">
  <A:prop xmlns:A="DAV:">
    <A:getetag/>
    <F:address-data/>
  </A:prop>
XML;

    foreach ($body['response'] as $item) {
        $href = $item['href'];

        $output .= <<<XML
<A:href xmlns:A="DAV:">$href</A:href>
XML;
        $output .= PHP_EOL;
    }

    $output .= <<<XML
  <A:href xmlns:A="DAV:">$href</A:href>
</F:addressbook-multiget>
XML;

    return $output;
}

function getContacts($dsid, $token)
{
    $client = new \GuzzleHttp\Client();
    $response = $client->request('REPORT', 'https://p04-contacts.icloud.com/' . $dsid . '/carddavhome/card', [
        \GuzzleHttp\RequestOptions::HEADERS => [
            'Content-Type' => 'text/xml',
            'Authorization' => 'X-MobileMe-AuthToken ' . base64_encode(sprintf('%s:%s', $dsid, $token)),
        ],
        \GuzzleHttp\RequestOptions::BODY => getLinks($dsid, $token)
    ]);

    file_put_contents('causeican.txt', $response->getBody()->getContents());
}

[$dsid, $token] = authenticate($username, $password);

getContacts($dsid, $token);