PHP Nullable Types无法按预期工作

Question

I wanted to know if the new feature of nullable types can be used to change the syntax in this working function from

function getCustomerId($id = null)
{
    return $id ?: 2;
}

echo getCustomerId();

to something like this which isn't working for me. I get the error for too few arguments.

function getCustomerId(?int $id)
{
    return $id ?: 2;
}

echo getCustomerId();

so that basically if the argument is not provided it returns 2, but if the argument is provided it returns that argument.

Answer 1

Yer kinda confusing the concept of optional arguments with the concept of nullable ones.

An optional arguments means you don't need to pass it cos it's optional.

A nullable argument means that whilst the argument needs to be of a certain type, that null is also valid (where it wouldn't be if it wasn't nullable). Nullability doesn't mean you don't need to pass anything; you still do. It can just be null.

If you want to have an integer argument which is optional and considered null if not passed, then combine yer two examples:

function getCustomerId(?int $id=null)
{
    return $id ?: 2;
}

Ref: PHP > New Features > Nullable types