PHP types before function arguments, good or bad?

Question

is there any advantage to providing types for arguments:

public static function DoStuff( string $str ) {
    echo $str;
}

in comparison to not using them?

public static function DoStuff( $str ) {
    echo $str;
}

Could it possibly run faster if I declare my types?

Answer 1

You cannot (with current versions of PHP) specify scalar types, such as string or int. You can only specify a class/interface, or array.

Relevant page of the manual: Type Hinting.

I see at least one great advantage of using type hinting: readability. It's easier to see what kind of parameter a function/method expects.

Some will see this as a drawback that if you don't respect a type hint and pass some not-type-valid parameter, you'll get a catchable fatal error. However,

• I personally think it forces the developer to respect your interfaces more
• It allows your code to just work with the received parameters.
• The generated error is catchable

If your question is about speed:

• Making the decision of using type hints or not using type hints should not be the result of performances considerations. You should use or not use the feature.
• Even if there is some performance impact, it should be pretty minimal. I would say there are many parts of your code that you should optimize before considering this.

In conclusion, a personal opinion: I quite often use those type hints, just so:

• People using my code know what they are expected to pass in (they don't always read the documentation...)
• If they don't do what is expected, it fails; hard; in a way they immediately notice
• My code doesn't have to check if the received parameter is of the right type: I know it is, as PHP enforces that for me.