<PixiSetItemBuyingInfoXMLPost200TextXmlResponse>
  <ItemKey>0</ItemKey>
  <ItemNrInt>string</ItemNrInt>
  <EAN>string</EAN>
  <MinStockQty>string</MinStockQty>
  <MinOrderQty>string</MinOrderQty>
  <SupplierCode>string</SupplierCode>
  <TargetStock>string</TargetStock>
  <SafetyStock>string</SafetyStock>
  <PackingUnit>string</PackingUnit>
</PixiSetItemBuyingInfoXMLPost200TextXmlResponse>

POST https://apigateway.descartes.com/tms/pixi/
Content-Type: text/xml; charset=utf-8
# echo -n '{{username}}:{{password}}' | base64 | pbcopy
Authorization: Basic {{token}}

<?xml version="1.0" encoding="UTF-8"?>
<SOAP-ENV:Envelope xmlns:SOAP-ENV="http://schemas.xmlsoap.org/soap/envelope/"
                   xmlns:ns1="https://apigateway.descartes.com/tms/pixi/"
                   xmlns:xsd="http://www.w3.org/2001/XMLSchema"
                   xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
                   SOAP-ENV:encodingStyle="http://schemas.xmlsoap.org/soap/encoding/">
    <SOAP-ENV:Body>
        <ns1:pixiSetItemBuyingInfoXML>
            <BuyingXML xsi:type="xsd:string">See Additional Information</BuyingXML>
        </ns1:pixiSetItemBuyingInfoXML>
    </SOAP-ENV:Body>
</SOAP-ENV:Envelope>

<?php

getPixiSoapClientResponse('pixiSetItemBuyingInfoXML', [
    'BuyingXML' => 'See Additional Information', // string
]);

function getPixiSoapClientResponse(string $method, array $arguments = [])
{
    $soapArguments = [];
    foreach ($arguments as $key => $value) {
        $soapArguments[] = new SoapVar($value, null, '', '', $key);
    }

    $soapClient = new SoapClient(null, [
        'login' => '...',
        'password' => '...',
        'uri' => 'https://apigateway.descartes.com/tms/pixi/',
        'location' => 'https://apigateway.descartes.com/tms/pixi/',
    ]);

    return $soapClient->__call($method, $soapArguments);
}