I've created an app with PHP5-xmlrpc and I'm using ripcord to connect to my Odoo webservice.
It worked fine with php5, but since my update to php7, the following happens:

$common = ripcord::client(ODOO_URL . "/xmlrpc/2/common") //create a connection
$uid = $common->authenticate(ODOO_DB, $user, $pass, []); //this call fails

The error I'm getting is Fatal error: xmlrpc_encode_request(): XML-RPC doesn't support circular references in [PATH]/ripcord_client.php on line 226

This line is $request = xmlrpc_encode_request( $name, $args, $this->_outputOptions ); and the values are:

$name => 'authenticate'  
$args => Array (
            [0] => [db_name]
            [1] => [login]
            [2] => [password]
            [3] => Array ()
         )

$this->_outputOptions => Array (
            [output_type] => xml
            [verbosity] => pretty
            [escaping] => Array (
                    [0] => markup
                )
            [version] => xmlrpc
            [encoding] => utf-8
        )

Some suggestions would be appreciated.