Error in Class DOMDocument

Hello,

I′d like to test the SSO Plug-In today, but I′ve got the following error-message, when I try to access the login page:

Fatal error: Class ‘DOMDocument’ not found in /srv/www/htdocs/wp-content/plugins/saml-20-single-sign-on/saml/lib/SAML2/Message.php on line 342

public function toUnsignedXML() {

		$this->document = new DOMDocument();

		$root = $this->document->createElementNS(SAML2_Const::NS_SAMLP, 'samlp:' . $this->tagName);
		$this->document->appendChild($root);

		/* Ugly hack to add another namespace declaration to the root element. */
		$root->setAttributeNS(SAML2_Const::NS_SAML, 'saml:tmp', 'tmp');
		$root->removeAttributeNS(SAML2_Const::NS_SAML, 'tmp');

		$root->setAttribute('ID', $this->id);
		$root->setAttribute('Version', '2.0');
		$root->setAttribute('IssueInstant', gmdate('Y-m-d\TH:i:s\Z', $this->issueInstant));

		if ($this->destination !== NULL) {
			$root->setAttribute('Destination', $this->destination);
		}

		if ($this->issuer !== NULL) {
			SAML2_Utils::addString($root, SAML2_Const::NS_SAML, 'saml:Issuer', $this->issuer);
		}

		return $root;
	}

And I′ve another question. My administrator need to get information like “Identifier” and a “URL endpoint” (something like https://…. .saml) to set it up in the IdP. Where can I find these information?

Best regards
Hugo

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