Problems to extract text from a PDF/A file

For machine learning purposes (php-ml), I need to extract the raw text from lots of PDF files.

But unfortunately, for few of them, I was unable to get the text because they are using "stream" on their pdf source, like this one.

<?php

include 'vendor'.DIRECTORY_SEPARATOR.'autoload.php';

// Parse pdf file and build necessary objects.
$parser = new \Smalot\PdfParser\Parser();
$pdf    = $parser->parseFile('pdfa.pdf');
 
$text = $pdf->getText();
echo $text;

The result is something like this:

https://i.imgur.com/xa8GBjS.png

Start by reproducing the report with the linked PDF/A file and the shown Parser::parseFile() and getText() calls. Inspect how the parser handles PDF streams and compare the extracted result with the source document. Done means the reported PDF/A file yields its raw text without breaking existing parsing behavior.