Can we consider DateTimeImmutable a primitive type?

Posted on by Matthias Noback

During a workshop we were discussing the concept of a Data Transfer Object (DTO). The main characteristic of a DTO is that it holds only primitive-type values (strings, integers, booleans), lists or maps of these values including "nested" DTOs. Not sure who came up with this idea, but I'm using it because it ensures that the DTO becomes a data structure that only enforces a schema (field names, the expected types, required fields, and optional fields), but doesn't enforce semantics for any value put into it. That way it can be created from any data source, like submitted form values, CLI arguments, JSON, XML, Yaml, and so on. Using primitive values in a DTO makes it clear that the values are not validated. The DTO is just used to transfer or carry data from one layer to the next. A question that popped up during the workshop: can we consider DateTimeImmutable a primitive-type value too? If so, can we use this type inside DTOs?

I thought it was an interesting question to explore. I'd like to say "No" immediately, but why?

Is it a DTO or a Value Object?

Posted on by Matthias Noback

A common misunderstanding in my workshops (well, whose fault is it then? ;)), is about the distinction between a DTO and a value object. And so I've been looking for a way to categorize these objects without mistake.

A step-debugger for the PHP AST

Posted on by Matthias Noback

When you're learning to write custom rules for PHPStan or Rector, you'll have to learn more about the PHP programming language as well. To be more precise, about the way the interpreter parses PHP code. The result of parsing PHP code is a tree of nodes which represents the structure of the code, e.g. you'll have a Class definition node, a Method definition node, and within those method Statement nodes, and so on. Each node can be checked for errors (with PHPStan), or automatically refactored in some way (with Rector).

The tree of nodes is called Abstract Syntax Tree, and a successful PHPStan or Rector rule starts with selecting the right nodes from the tree and "subscribing" your rule to these nodes. A common approach for this is to start var_dump-ing or echo-ing nodes inside your new rule, but I've found this to be quite tedious. Which is why I've created a simple command-line tool that lets you inspect the nodes of any given PHP file.