Sample Call

<?php
// SOAP_CLIENT_BASEDIR - folder that contains the PHP Toolkit and your WSDL
// $USERNAME - variable that contains your Salesforce.com username (must be in the form of an email)
// $PASSWORD - variable that contains your Salesforce.com password

define("SOAP_CLIENT_BASEDIR", "../../soapclient");
require_once (SOAP_CLIENT_BASEDIR.'/SforcePartnerClient.php');
require_once ('../userAuth.php');

try {
  $mySforceConnection = new SforcePartnerClient();
  $mySoapClient = $mySforceConnection->createConnection(SOAP_CLIENT_BASEDIR.'/partner.wsdl.xml');
  $mylogin = $mySforceConnection->login($USERNAME, $PASSWORD);

/*--------------------------------------------------------\
| Please manage the values for OBJECT ID from file 
| userAuth.php
\--------------------------------------------------------*/

  $fieldsToUpdate = array (
  'FirstName' => 'testupdate',
  'City' => 'testupdateCity',
  'Country' => 'US'
  );
  $sObject1 = new SObject();
  $sObject1->fields = $fieldsToUpdate;
  $sObject1->type = 'Lead';
  $sObject1->Id = $UPDATEOBJECTID1;

  $fieldsToUpdate = array (
  'FirstName' => 'testupdate',
  'City' => 'testupdate',
  'State' => 'testupdate',
  'Country' => 'US'
  );
  $sObject2 = new SObject();
  $sObject2->fields = $fieldsToUpdate;
  $sObject2->type = 'Lead';
  $sObject2->Id = $UPDATEOBJECTID2;
  $sObject2->fieldsToNull = array('Fax', 'Email');

  $response = $mySforceConnection->update(array ($sObject1, $sObject2));

  print_r($response);

} catch (Exception $e) {
  print_r($mySforceConnection->getLastRequest());
  echo $e->faultstring;
}
?>

Sample Output