Appending PDF Files in PHP with Base64 - php

Question

I have a series of base64 PDF Files that I would like to merge together. Currently I am using file_get_contents() and with PHPMailer can attach each of them separately.
$woFile = file_get_contents($url);
$invoiceFile = file_get_contents($invPDF64);
$tsFile = file_get_contents($tsPDF64);
...
$mail->AddStringAttachment($woFile, "1.pdf", "base64", "application/pdf");
$mail->AddStringAttachment($invoiceFile, "2.pdf", "base64", "application/pdf");
$mail->AddStringAttachment($tsFile, "3.pdf", "base64", "application/pdf");
All the examples I've seen online such as FPDF require the file to be locally downloaded, at least from what I saw. Is there a way to append each of these PDF files into one, and then have that attached to the email?
Thanks in advance!

Answer 1

I'm not sure if you specifically need to merge the PDFs into one PDF, or if you just want one file. Here are options for both:
If you want to merge all PDFs into a single PDF file, then this is a duplicate question. You mention not wanting to have a local file, but this may be an unreasonable constraint (e.g., memory issues with large PDFs). Use temporary files as appropriate and clean up after yourself.
If you just want a single file, consider putting the files into a ZIP archive and sending that. You might also like the ZipStream library for this purpose. Here's some minimal code using the native library:
$attachmentArchiveFilename = tempnam('tmp', 'zip');
$zip = new ZipArchve();
# omitting error checking here; don't do it in production
$zip->open($attachmentArchiveFilename, ZipArchve::OVERWRITE);
$zip->addFromString('PDFs/first.pdf', $woFile);
$zip->addFromString('PDFs/second.pdf', $invoiceFile);
$zip->addFromString('PDFs/third.pdf', $tsFile);
$zip->close();
$mail->addAttachment($attachmentArchiveFilename, 'InvoicePDFs.zip');
# be sure to unlink/delete/remove your temporary file
unlink( $attachmentArchiveFilename );