Set multiple extraFields with one html_query

[ghost]

I am suggesting to solve j0k3r/graby#271 by

1. allowing the xpath function to return multiple results, e.g. a fixed number passed as argument
   

   guzzle-site-authenticator/lib/ExpressionLanguage/AuthenticatorProvider.php

   Lines 71 to 96 in b5f1ebd

   	'xpath',
   	function () {
   	throw new Exception('Not supported');
   	},
   	function (array $arguments, $xpathQuery, $html) {
   	$useInternalErrors = libxml_use_internal_errors(true);
   	$doc = new \DOMDocument();
   	$doc->loadHTML((string) $html, LIBXML_NOCDATA | LIBXML_NOWARNING | LIBXML_NOERROR);
   	$xpath = new \DOMXPath($doc);
   	$domNodeList = $xpath->query($xpathQuery);
   	if (0 === $domNodeList->length) {
   	return '';
   	}
   	$domNode = $domNodeList->item(0);
   	libxml_use_internal_errors($useInternalErrors);
   	if (null === $domNode || null === $domNode->attributes) {
   	return '';
   	}
   	return $domNode->attributes->getNamedItem('value')->nodeValue;

2. setting multiple fields at once by splitting the fieldName variable using a predefined or configurable separator
   

   guzzle-site-authenticator/lib/Authenticator/LoginFormAuthenticator.php

   Line 105 in b5f1ebd

   $extraFields[$fieldName] = $fieldValue;

   
   Do you have any comments or objections to this approach?

[ghost]

This would allow setting multiple headers using a single request, e.g. login_extra_fields: login_ticket;_csrf=@=xpath('//input[@id="login_ticket_login-form" or @id="_csrf_login-form"]/@value', request_html('https://id.sueddeutsche.de/login'))
A potential downside of this approach is that it assumes the order of the nodes in question to be fixed.

[ghost]

Alternatively one could include the field names in the XPath expression and parse its output. This would solve the order problem without complicating the logic too much.