// Create client class using credentials received from PostNL.
$client = new Postnl(
    12345678,   // Customer number
    'ABCD',     // Customer code
    'Acme BV',  // Customer name
    'Acme',     // Username
    'Password', // Password
    123456,     // Collection location
    'CD1234',   // Globalpack
    true        // Whether to use PostNL's sandbox environment.
);

/**
 * Jan Smit
 * Smit & Zonen
 * Hoofdstraat 1A
 * 1234 AB Heikant
 * The Netherlands
 */
$receiverAddress = ComplexTypes\Address::create()
    ->setAddressType('01')
    ->setFirstName('Jan')
    ->setName('Smit')
    ->setCompanyName('Smit & Zonen')
    ->setStreet('Hoofdstraat')
    ->setHouseNr('1')
    ->setHouseNrExt('A')
    ->setZipcode('1234AB')
    ->setCity('Heikant')
    ->setCountrycode('NL');

$senderAddress = ComplexTypes\Address::create()
    ->setAddressType('02')
    ->setFirstName('Robert')
    ->setName('Jansen')
    ->setCompanyName('Jansen & Janssen')
    ->setStreet('Hoofdstraat')
    ->setHouseNr('999')
    ->setHouseNrExt('B')
    ->setZipcode('1234AB')
    ->setCity('Heikant')
    ->setCountrycode('NL');

// Request a barcode from PostNL.
$barcode = $client->generateBarcodeByDestination($receiverAddress->getCountryCode());

// Create a shipment.
$shipment = ComplexTypes\Shipment::create()
    ->setAddresses(new ComplexTypes\ArrayOfAddress([
        $receiverAddress,
        $senderAddress,
    ]))
    ->setBarcode($barcode)
    ->setDimension(ComplexTypes\Dimension::create()
        ->setWeight(5000) // Weight in g
        ->setWidth(215)   // Width in mm
        ->setLength(305)  // Length in mm
        ->setHeight(280)  // Height in mm
    )
    ->setProductCodeDelivery('3085');

// Generate label and confirm shipment.
$result = $client->generateLabel($shipment);

// Save the label PDFs locally.
$i = 0;
foreach ($result->getLabels() as $label) {
    $i++;
    $file = new \SplFileObject("label{$i}.pdf", 'w');
    $file->fwrite($label->getContent());
}