Bridging the Gap between PHP 5.3 and 8.2

This week I got finally got involved with maintaining the languishing TCPDF library on Github. Long overdue. Embarrassingly long overdue, since I’ve based one of my businesses on this open source gem for nearly ten years now.

The author, Nicola Asuni, has been working for many years on a successor to TCPDF, but it is stalled… likely due to the usual reasons: life and cash. I can relate. I’ve been sitting on a huge WP plugin project for two years now, desperately trying to move it forward while life happens and I’m forced to prioritize support for my paying customers.

A couple years ago an eager young programmer, William Desportes, hopped onto the TCPDF GitHub and made an incredible fork which would have really helped bring TCPDF into this decade. It needed massaging to work with PHP 8.0+ and he gave it a rub. However, understandably, the original author reminded Desportes he was already working on a new version, and that helping with/watching the fork would just be too much. Probably annoying, too.

Asuni invited Desportes to be a project contributor on the old TCPDF. Since, Desportes has been the most active, if not the only active contributor to TCPDF, with Asuni popping in to approving PRs. And largely thanks to Desportes, the library is keeping up with huge PHP updates.

Anyway, in my testing I discovered a bug in TCPDF while testing with PHP 8.2:

Warning: use of “self” in callables is deprecated

Uh oh. This means we cannot use self::method as callables inside functions that call them, like array_map(), any longer in PHP 9.0. We also cannot do a thing where we name the class and method in an array, e.g. array('class', 'method')

We have a little bit of time to fix this before PHP 9.0 comes out, but everyone hates a warning so best fix it now. An instant replacement for using self::method would look like:

self::class . "::method"

Another option could be something like:

[self::class, "method"]

Neither of these will work with PHP 5.3. The moment PHP 5.3 sees ::class, it breaks. The moment PHP 5.3 and 5.4 see square brackes, they break.

So how the hell do we get our fix to work with both PHP 8.2 AND PHP 5.3 (TCPDF is stated compatible down to PHP 5.3)?


Corresponding Pull Request:

I was pretty excited to patch this up quickly, but my initial fix was no good. Somehow I got lost in testing and was led to believe it worked in PHP 5.3 But ::class isn’t a thing until PHP 5.5. Back to the drawing board! I do not and cannot use a test for PHP version because:

  • Moving the code for newer versions to newly created files is cumbersome and feels backward-moving
  • Again, the instant PHP 5.3 sees code it doesn’t recognize, e.g. ::class or [] notation, it just breaks

So I spend some time testing various things, trying to find a reference to the static method that both PHP 5.3 and PHP 8.2 will use unbegrudgingly. And after trying various methods and going back and forth between 5.3 and 8.2 and all versions in between, I find that using `get_called_class` works as a replacement for array(‘TCPDF_FONTS’, ‘unichrUnicode’), especially these static methods I’m looking to resolve in TCPDF. Thus

return array_map(array('TCPDF_FONTS', 'unichrUnicode'), $ta);


 return array_map(get_called_class() . '::unichrUnicode', $ta );

I’ve sorted it out, but in the process I sorta lose my marbles and start posting about nuts on Github. I’m battling the frustration of WHY ARE WE STILL coding for PHP 5.3 when it was deprecated 9 years ago?! I’m also battling some imposter syndrome. Like, why am I the chosen one today? I hardly know how to use Github! How can I be one of the only people left working on this massively popular library? Will this work for everyone the way it worked for me in test after test, or will this be my “Carrie at the prom” moment, having finally just stuck out my neck on Github? Time will tell! But for now, it works, so… you’re welcome. ☺️