$client = new SoapClient($WSDL, array(
        'authentication' => 'SOAP_AUTHENTICATION_BASIC',
        'login' => $login,
        'password'=> $password,
        'trace' => 1
    ));

//SOAP-ERROR: Parsing Schema: element 'http://*****/schema:List' already defined

<wsdl:import location="http://*****?wsdl=Schema_output.xsd" namespace="http://*****/schema">
    </wsdl:import>
    <wsdl:import location="http://*****?wsdl=Schema_input.xsd" namespace="http://*****/schema_input">

<xsd:import namespace="http://*****/schema" schemaLocation="http://*****?xsd=Schema_output.xsd"/>