Exemplo com form

<?php 
        //Data, connection, auth
        $dataFromTheForm = $_POST['fieldName']; // request data from the form
        $soapUrl = "https://connecting.website.com/soap.asmx?op=DoSomething"; // asmx URL of WSDL
        $soapUser = "username";  //  username
        $soapPassword = "password"; // password

        // xml post structure

        $xml_post_string = '<?xml version="1.0" encoding="utf-8"?>
                            <soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xmlns:xsd="http://www.w3.org/2001/XMLSchema" xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
                              <soap:Body>
                                <GetItemPrice xmlns="http://connecting.website.com/WSDL_Service"> // xmlns value to be set to your's WSDL URL
                                  <PRICE>'.$dataFromTheForm.'</PRICE> 
                                </GetItemPrice >
                              </soap:Body>
                            </soap:Envelope>';   // data from the form, e.g. some ID number

           $headers = array(
                        "Content-type: text/xml;charset=\"utf-8\"",
                        "Accept: text/xml",
                        "Cache-Control: no-cache",
                        "Pragma: no-cache",
                        "SOAPAction: http://connecting.website.com/WSDL_Service/GetPrice", 
                        "Content-length: ".strlen($xml_post_string),
                    ); //SOAPAction: your op URL

            $url = $soapUrl;

            // PHP cURL  for https connection with auth
            $ch = curl_init();
            curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, 0);
            curl_setopt($ch, CURLOPT_URL, $url);
            curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
            curl_setopt($ch, CURLOPT_USERPWD, $soapUser.":".$soapPassword); // username and password - declared at the top of the doc
            curl_setopt($ch, CURLOPT_HTTPAUTH, CURLAUTH_ANY);
            curl_setopt($ch, CURLOPT_TIMEOUT, 10);
            curl_setopt($ch, CURLOPT_POST, true);
            curl_setopt($ch, CURLOPT_POSTFIELDS, $xml_post_string); // the SOAP request
            curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);

            // converting
            $response = curl_exec($ch); 
            curl_close($ch);

            // converting
            $response1 = str_replace("<soap:Body>","",$response);
            $response2 = str_replace("</soap:Body>","",$response1);

            // convertingc to XML
            $parser = simplexml_load_string($response2);
            // user $parser to get your data out of XML response and to display it.
    ?>

Exemplo sem form

<?php
  $soap_request  = "<?xml version=\"1.0\"?>\n";
  $soap_request .= "<soap:Envelope xmlns:soap=\"http://www.w3.org/2001/12/soap-envelope\" soap:encodingStyle=\"http://www.w3.org/2001/12/soap-encoding\">\n";
  $soap_request .= "  <soap:Body xmlns:m=\"http://www.example.org/stock\">\n";
  $soap_request .= "    <m:GetStockPrice>\n";
  $soap_request .= "      <m:StockName>IBM</m:StockName>\n";
  $soap_request .= "    </m:GetStockPrice>\n";
  $soap_request .= "  </soap:Body>\n";
  $soap_request .= "</soap:Envelope>";
 
  $header = array(
    "Content-type: text/xml;charset=\"utf-8\"",
    "Accept: text/xml",
    "Cache-Control: no-cache",
    "Pragma: no-cache",
    "SOAPAction: \"run\"",
    "Content-length: ".strlen($soap_request),
  );
 
  $soap_do = curl_init();
  curl_setopt($soap_do, CURLOPT_URL, "http://localhost/php-soap-curl/soap-server.php" );
  curl_setopt($soap_do, CURLOPT_CONNECTTIMEOUT, 10);
  curl_setopt($soap_do, CURLOPT_TIMEOUT,        10);
  curl_setopt($soap_do, CURLOPT_RETURNTRANSFER, true );
  curl_setopt($soap_do, CURLOPT_SSL_VERIFYPEER, false);
  curl_setopt($soap_do, CURLOPT_SSL_VERIFYHOST, false);
  curl_setopt($soap_do, CURLOPT_POST,           true );
  curl_setopt($soap_do, CURLOPT_POSTFIELDS,     $soap_request);
  curl_setopt($soap_do, CURLOPT_HTTPHEADER,     $header);
 
  if(curl_exec($soap_do) === false) {
    $err = 'Curl error: ' . curl_error($soap_do);
    curl_close($soap_do);
    print $err;
  } else {
    curl_close($soap_do);
    print 'Operation completed without any errors';
  }
?>

gistfile1.txt

<?php
$xml = '<?xml version="1.0" encoding="utf-8"?>'.
    '<soap:Envelope xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"'.
    ' xmlns:xsd="http://www.w3.org/2001/XMLSchema"'.
    ' xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">'.
        '<soap:Body>'.
            '<GetShirtInfo xmlns="http://api.soap.website.com/WSDL_SERVICE/">'.
                '<ItemId>15</ItemId>'.
            '</GetShirtInfo>'.
        '</soap:Body>'.
    '</soap:Envelope>';

$url = "https://api.soap.website.com/soap.asmx?wsdl";

$ch = curl_init();
curl_setopt($ch, CURLOPT_URL, $url);
curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, false);
curl_setopt($ch, CURLOPT_SSL_VERIFYHOST, 0);

$headers = array();
array_push($headers, "Content-Type: text/xml; charset=utf-8");
array_push($headers, "Accept: text/xml");
array_push($headers, "Cache-Control: no-cache");
array_push($headers, "Pragma: no-cache");
array_push($headers, "SOAPAction: http://api.soap.website.com/WSDL_SERVICE/GetShirtInfo");
if($xml != null) {
    curl_setopt($ch, CURLOPT_POSTFIELDS, "$xml");
    array_push($headers, "Content-Length: " . strlen($xml));
}
curl_setopt($ch, CURLOPT_USERPWD, "user_name:password"); /* If required */
curl_setopt($ch, CURLOPT_POST, true);
curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
$response = curl_exec($ch);
$code = curl_getinfo($ch, CURLINFO_HTTP_CODE);
curl_close($ch);
?>