函数参数“array”，“string”和“boolean”如何在PHP中工作？

Question

I'm making a program that will only accept a boolean value as parameter. I thought I could instanceof to do this, but it does not work as I expected.

function test (boolean $param) {
    echo $param;
}
test(true);

When I use it in my program, I get following error message:

Argument 1 passed to test() must be an instance of boolean

Is instanceof the right method to do this and how does it work?

Answer 1

As per the manual on type-declarations, it's stated that you need to use bool instead of boolean when type-declaring for a boolean value. This also requires PHP-version 7.0.0 or higher.

function test (bool $param) {}
test(true);

If you are on a PHP version lower than 7.0.0, you cannot use the boolean type-declaration at all. However, you can check if a boolean argument was supplied by using is_bool($param), then return false, null or throw an exception instead, and deal with it that way. You can also issue a user-warning (by trigger_error()) if you think its appropriate.

• PHP.net on type declarations
• PHP.net on is_bool()
• PHP.net on trigger_error()