<?php

$wsdl   = "https://<your_web_service_url>?wsdl";
$client = new SoapClient($wsdl, array('trace'=>1));  // The trace param will show you errors stack

// web service input params
$request_param = array(
    "param1" => $value1,
    "param2" => $value2,
    "param3" => $value3,
    "param4" => $value4
);

try
{
    $responce_param = $client->webservice_methode_name($request_param);
   //$responce_param =  $client->call("webservice_methode_name", $request_param); // Alternative way to call soap method
}
catch (Exception $e)
{
    echo "<h2>Exception Error!</h2>";
    echo $e->getMessage();
}

<?php
require_once('lib/nusoap.php');

$wsdl   = "http://<your_web_service_url>?wsdl";
$client = new nusoap_client($wsdl, 'wsdl');

// Input params
$username = "username";
$password = "pass";

// In this demo, we use json data , you can use any other data format for same
$json     = '{"param1":"value1","param2":"value2"}';

$client->setCredentials($username, $password);
$error = $client->getError();

if ($error)
{
    echo $error; die();
}

$action = "webservice_methode_name"; // webservice method name

$result = array();

if (isset($action))
{
    $result['response'] = $client->call($action, $json);
}

echo "<h3>Output : </h3>";
echo $result['response'];
echo "<h2>Request</h2>";
echo "<pre>" . htmlspecialchars($client->request, ENT_QUOTES) . "</pre>";
echo "<h2>Response</h2>";
echo "<pre>" . htmlspecialchars($client->response, ENT_QUOTES) . "</pre>";