Inexplicable type hinting in PHP code

Question

I'm analyzing some PHP code which is running on a server I don't have full access to. I can read the phpinfo though. The code seems to run fine on the server. In my local environment I just can't get the code to run as I get a "Catchable Fatal Error" at some call of a method using type hinting.

someMethod(string $str) {
  // Do something...
}

The error says the following: "Argument 1 passed to ... must be an instance of path\of\namespace\string, string given ...".

There is no use keyword with a string class nor can I find anything trough a grep command in the folders of the development environment.

Are there any PHP modules, extensions that can make such a type hinting work? The server and my development environment are using PHP 5.4.25.

What could the live system possibly provide to make such code run? Might it use some other programming language based on PHP like Hack? The rest of the code is pretty straight PHP!

Answer 1

You mention that there is no use statement or namespace declaration that alludes to a 'string' class in the code. Does the code use an Autoloader?

Two possible issues at hand here:

Paths - It is possible that the live environment has another path set up, and/or that a file/class is being loaded/searched for via this 'other path' (outside the code you may be looking at).

Error Handling - Another possible cause is if there is an error handler in the production environment that always returns true.

I had this exact issue where a type-hint wasn't resolving in development, but I didn't realize until we pushed it live and the error handler was no longer registered.

Obviously a fatal parse error can not be stopped, but it turns out a catch-able error can be ignored if the error handler returns true. And this is what I am putting my money on in your case.

Additionally, it is very important to note that there is no way to type-hint a scalar, as one user pointed out.

A simpler way to say it is "it is not possible to type-hint anything that can be represented by a string." This is due to the way in which PHP handles it's more primitive variables, they can all be type-cast to one another, and therefore (because 1, "1" and true can all be == 1, == '1' and == true) it is not actually possible for the interpreter as it is written to actually catch and enforce scalar type-hints.

Answer this question: Is that variable supposed to be $str = "something"; or $str = new string(); (ie, a string or an object)?

If it is supposed to be a string, remove the type-hint, as nothing in PHP allows this support (save for HHVM, but you would know this if you were using it).

Since you say you do not have access to the code, I suggest notifying someone who does.