Is there a Dependency Injection framework for PHP4?

Question

I'm stuck on a PHP 4 server, and I would like to start moving an old legacy project to modern Design Patterns, including Dependency Injection. Are there any dependency injection frameworks that will work with PHP 4?

Answer 1

I don't think a dependency injection framework will really work on PHP because of the way object-oriented programs are structured in it. First of all, it's not like C# or Java wherein the binaries are already there and you just have to find a way to instantiate this object and inject it into another. PHP has to load the class files and interpret them before it can use them. So if you have deep inheritance hierarchies with PHP I don't think that's a good idea.

Given that PHP is a scripting language, it's best to leverage it as that -- a scripting language. Which means, I would just make use of simple factory or builder methods to do something similar to dependency injection. I wouldn't burden it with a DI framework that will only add to the stuff the PHP runtime has to process for every web request (unless you do opcode caching, but there will still be overhead that's not incurred by web platforms for Java and .NET). If I have to change the objects that will be injected into objects or how they are created, it would be a simple task to just edit the script that contains the factory/builder methods. No need to recompile there anyway. So I have flexibility and I have a lightweight architecture that's suitable for the PHP way of doing things.

Answer 2

i found this (drip), but it looks like it hasn't been updated in a few years.

Answer 3

I wrote my own, but it's kind of hacky and relies on preloading everything, meaning it has serious performance penalties. I rewrote it in PHP5, and the __autoload function is a godsend.

Answer 4

Most dependency injection frameworks use reflection to determine dependencies. Since PHP4 doesn't have typehints, you can't really do this. Experiments have been made with using config files - Some times embedded in comments in the code (Often called annotations). While this works, I find it a bit clunky. In my opinion, you're better off using PHP's dynamic nature to your advantage, than to try and apply statically typed solutions to it. You can get a long way with hand-crafted factories. See for example this post on how.