How to overlay HTML generated PDF on top of existing PDF?

Question

I'm looking to start with an initial PDF file, one that has graphics and text, and then take some html code which has dynamic values for some user input, generate that as a PDF, hopefully either using the initial PDF as a background, OR somehow running a PHP script afterwards to "merge" both PDF where one acts as a background to another.

I have some code that renders an HTML formatted PDF: (using DOMPDF)

$initialpdf = file_get_contents('file_html.html');

$initialpdf = str_replace(array(
        '%replaceText1%',
        '%replaceText2%'
    ), array (
        $replaceText1,
        $replaceText2,
    ), $initialpdf);

$fp = fopen('file_html_new.html','w');
file_put_contents('file_html_new.html', $initialpdf);

require_once("dompdf/dompdf_config.inc.php");
spl_autoload_register('DOMPDF_autoload');
function pdf_create($html, $filename, $paper, $orientation, $stream=TRUE)
{
    $dompdf = new DOMPDF();
    $dompdf->set_paper($paper,$orientation);
    $dompdf->load_html($html);
    $dompdf->render();
    $pdf = $dompdf->output();
    @file_put_contents($filename . ".pdf", $pdf);
}
$filename = 'HTML_Generated_pdf';
$dompdf = new DOMPDF();
$html = file_get_contents('file_html_new.html'); 
pdf_create($html,$filename,'Letter','landscape');

The code above takes html file "file_html.html" and does string replacements with user input values, renders this as a new HTML file called "file_html_new.html" and then renders that AS a PDF.

I also have other PHP code that render a PDF by having a PDF as an initial source: (using FPDF)

<?php
ob_clean();
ini_set("session.auto_start", 0);
define('FPDF_FONTPATH','font/');
define('FPDI_FONTPATH','font/');
require('fpdf.php');
require('fpdi.php');

$pdf = new FPDI();
$pdf->setSourceFile("/home/user/public_html/wp-content/myPDF.pdf");
$tplIdx = $pdf->importPage(1);
$specs = $pdf->getTemplateSize($tplIdx);
$pdf->addPage($specs['h'] > $specs['w'] ? 'P' : 'L', 'Letter');
$pdf->useTemplate($tplIdx,  0, 0);

$pdf->SetFont('helvetica');
$pdf->SetXY(30, 30);
$pdf->Write(0, $replaceText1);
ob_end_clean();
$pdf->Output('New_Generated_PDF.pdf', 'F');
?>

This takes an already existing PDF, "myPDF.pdf", and uses it as a background, writing some passed in value to the document, and saving the newly produced document.

While this is essentially what I want to do, I need to work with html because the exact formatting for text gets rigorous and almost impossible to do just by plotting it in manually.

I'm open to using DOMPDF, FPDF, FPDI, TCPDF, or any other PHP resource in order to accomplish this.

Is there a way to fuse the two ways I have above?

Answer 1

For sure you can use different existing PDF documents with FPDI, too. This code should show you the concept (actually I guess that all page formats are A4 portrait):

<?php

$pdf = new FPDI();

// let's get an id for the background template
$pdf->setSourceFile('myPDF.pdf'); 
$backId = $pdf->importPage(1);

// iterate over all pages of HTML_Generated_pdf.pdf and import them
$pageCount = $pdf->setSourceFile('HTML_Generated_pdf.pdf');
for ($pageNo = 1; $pageNo <= $pageCount; $pageNo++) {
    // add a page
    $pdf->AddPage();
    // add the background
    $pdf->useTemplate($backId);
    // import the content page
    $pageId = $pdf->importPage($pageNo);
    // add it
    $pdf->useTemplate($pageId);
}

$pdf->Output();