<?php

// create XML...
$comprobante = new Comprobante();
$comprobante->Serie = "0A";
$comprobante->Folio = "11";
$comprobante->FormaPago = "03";
$comprobante->...

$emisor = new Emisor();
$emisor->Rfc = "XAXX010101000";
$emisor->Nombre = "Publico General";
$emisor->RegimenFiscal = "608";
$comprobante->Emisor = $emisor;

$cfdi = new Cfdv33($comprobante, $rutaCert, $rutaKey);
// This XML is already signed by the certificate and primary key
// Is ready to send to the favorite PAC
echo $cfdi->getXml();

<?php
// Declare utils
$utlXml = new XmlUtils();

// Get original string from the XML
$cadenaOriginal = $utlXml->GeneraCadenaOriginal(file_get_contents($pathXml));

// generated sign from original string, this add to the XML
$sello = $this->utlXml->GeneralSelloCfdi33($cadenaOriginal, file_get_contents($rutaKey), $claveKey);

<?php
// Certificate utilities declared
$utlCert = new CertificadoUtils();

// Get the bash from to certificate, this add to the XML
$certificado = $utlCert->GeneraCertificado2Pem(file_get_contents($rutaCert));

// Get the certificate number from file .cer, this add to the XML
$noCertificado = $utlCert->GetNumCertificado(file_get_contents($rutaCert));

<?php
// Certificate utilities declared
$utlCert = new CertificadoUtils();
$utlCommons = new CommonsUtils();

// Get date format requiered for the XML
echo $utlCommons->GetFechaActualCFDI();
// Out: 2019-10-18T13:21:36

// Replace characters especial
echo $utlCommons->ReplaceEncodeUtf8('Asociados&Otros');
// Out: Asociados&amp;Otros

// Formato to numbers
echo $utlCommons->FormatNumber(100, 2)
// Out: 100.00

// Validate certificate
echo $utlCert->ValidateCertificado(file_get_contents($rutaCert));
// Out: Certificado emitido por el SAT.

// Validate file primary key
echo  $utlCert->ValidatePrivateKey(file_get_contents($rutaKey));
// Out: Certificado emitido por el SAT.