SimpleSAML_XHTML_IdPDisco::getSelectedIdP PHP Method

    protected function getSelectedIdP()
    {
        /* Parameter set from the Extended IdP Metadata Discovery Service Protocol, indicating that the user prefers
         * this IdP.
         */
        if (!empty($this->setIdPentityID)) {
            return $this->validateIdP($this->setIdPentityID);
        }
        // user has clicked on a link, or selected the IdP from a drop-down list
        if (array_key_exists('idpentityid', $_GET)) {
            return $this->validateIdP($_GET['idpentityid']);
        }
        /* Search for the IdP selection from the form used by the links view. This form uses a name which equals
         * idp_<entityid>, so we search for that.
         *
         * Unfortunately, php replaces periods in the name with underscores, and there is no reliable way to get them
         * back. Therefore we do some quick and dirty parsing of the query string.
         */
        $qstr = $_SERVER['QUERY_STRING'];
        $matches = array();
        if (preg_match('/(?:^|&)idp_([^=]+)=/', $qstr, $matches)) {
            return $this->validateIdP(urldecode($matches[1]));
        }
        // no IdP chosen
        return null;
    }