Support typed variables

[arashdeveloper1380]

Description

When I want to make a variable, I want to put its type as in other languages

like :

string $name = "arash"
int $age = 23
or ...

[SakiTakamachi]

Hi, an RFC is needed to add this functionality.

To do this, you need to discuss the feature on the internal mailing list.

If you want to know the RFC procedure:
https://wiki.php.net/rfc/howto

[cmb69]

To do this, you need to discuss the feature on the internal mailing list.

Right, especially since such dicussions happened already (e.g. https://externals.io/message/119470).

[iluuu1994]

It's also been raised here before:

#9962
#11419

Introducing types for variables is a technical challenge, 1. because it requires more type checks and will likely slow things down, unless we also improve the optimizer, and 2. because it implies scoping. It is also questionable, given that most modern languages are moving away from explicit typing, and type inference in static analysis is very good, and can deal with variables changing types very well.

If you're still convinced this is a good idea, please collect your thoughts in an e-mail and send it to the internals mailing list (https://www.php.net/mailing-lists.php).

[stanislav-oop]

Well, even if the variable itself can not be typed, we can still have typed assignment but with the same syntax.
Example:

string $name = "arash";
int $name = 23;

This is valid because its not the variable which gets type, its an assignment that is "validated"

int test = "hey";
this will fail

and most importantly

?SomeClass $someClass = $array['someClassInstance']; will validate the class, in other words just work like a function parameter type checks. This is great also for the foreach

foreach($array as SomeClass $item)

[iluuu1994]

Historically, variable types are specified to calculate the size of the stack frame for the current function. Since PHP is a dynamically typed language and every variable essentially has the same size, it does not need to know the exact type the variable will have. If you really want to be sure a variable has the right type, you can use an assert(). However, the type of most variables can be inferred by static analysis tools like PHPStan, which will report an error if it is used in some invalid way. Most compiled languages are now moving towards type inference to reduce boilerplate (e.g. C# with var, C/C++ with auto, Swift, Rust, Kotlin, many more). I would find it weird for a loosely typed language to be more verbose in terms of typing, just for the sake of being more typed.

There is also some overlap with the as keyword described in https://wiki.php.net/rfc/pattern-matching#as_keyword. It would achieve what you're asking for, be it with different syntax.

$name = "arash" as string;
$name = 23 as int;
// Fail
$test = "hey" as int;

[stanislav-oop]

Well, the most use for me is the type hinting for the IDE. Type check is somewhat secondary.
/* @var $person Person */
foreach ($array as $person) {
or
foreach ($array as Person $person) {

[iluuu1994]

A good IDE can do type inference. Even if we were to add this featue, it doesn't mean a bad IDE starts working any better.