How can I create a PHP program that converts ZPL to PDF without using external services like Labelary?

I'm trying to create a PHP program that can convert ZPL (Zebra Programming Language) to PDF. However, I haven't found much information on how to do this directly in PHP. Most of the resources I've come across point me to services like Labelary.

Since services like Labelary can render ZPL, I believe it's possible, but I'm curious about how they are doing it. I wonder if it's a custom implementation or if they're using some specific libraries. Could someone provide some guidance on how to approach this? What would be the first steps? And how long would it take to build this from scratch?

And if not in PHP, in what other language is it possible?

I did some research and found that I need to first parse the ZPL so the PHP application can understand all the ZPL commands for drawing the label. And it also seems like the ZPL needs to be converted into an image first before it can be turned into a PDF. But I’m not sure if I'm correct on this or if there's a better method to handle ZPL in PHP, or perhaps in another language. So far, I haven’t found any specific libraries or tools to implement this directly.