Is it possible to write strictly typed PHP code?

Question

For example, is it possible to write code like this:

int $x = 6;
str $y = \"hello world\";
bool $z = false;
MyObject $foo = new MyObject();

Answer 1

Something you might try in order to simulate a poor man's strict type checking is using assert() to force the output to be of a particular type before you return it:

/**
 * Get Balance
 *
 * @return int
 */
function getBalance()
{
    /* blah blah blah */
   $out = 555; //Or any numeric value
   assert('is_int($out)');
   return $out;
}

So you keep your assertions active all throughout development and testing, sort of like the checks the compiler does at compile-time.

Granted, the assert() page is keen to assert that you shouldn't use assertions to check input parameters, but rather use normal conditionals to check them.

This answer had what I thought was a good rule:

The rule of thumb which is applicable across most languages (all that I vaguely know) is that an assert is used to assert that a condition is always true whereas an if is appropriate if it is conceivable that it will sometimes fail.

If you're simulating strict type-checking (writing your code to viciously maintain types; not trying to validate input from the outside), then you ought to be certain what the type is unless you've made a mistake.

Update:

There's also this: http://hacklang.org/ Facebook's PHP-based language with static typing.

Answer 2

You could use h2tp transpiler to transpile HACK code to PHP:

You can do this thanks to Facebook Team and HACK Language.

Visit http://hacklang.org and http://hhvm.com for more info.

If you want to code directly in Hack + HHVM environment you can also use Facebook's internal IDE Nuclide

Answer 3

In PHP 7 are implemented "Scalar Type Declarations", e.g.:

public function getBalance(): int {
    return 555;
}

You need to declare, that you will use strict types:

<?php
    declare(strict_types=1);

    function sum(int $a, int $b): int {
        return $a + $b;
    }

    sum(1, 2);
?>

More information: https://wiki.php.net/rfc/scalar_type_hints_v5

Answer 4

No. That syntax will not work.

You could, theoretically, come up with a system of objects that enforced their own sort of strict typing, but it wouldn't perform and ...why would you want to, anyway?

If you need strict typing, use a strictly typed language.

Answer 5

Perhaps you should try this PHP extension https://github.com/krakjoe/strict. Support for the following types is introduced:

• string
• integer, int
• float, double
• boolean, bool
• resource

Answer 6

PHP is not strictly typed, so no. That said, it does support limited type hinting on functions - that's as close as it gets.