"array" here is a type name. It is not directly related to the syntax for constructing an array. After all, you do the typehints like this:

    function test(array $arr);
    function test(SomeClass $obj);
    function test(callable $callback);

And not like this:

    function test(array() $arr);
    function test(new SomeClass $obj);
    function test(function() {} $callback);

"array" is a type, while "array()", "array('a', 'b')", "[]" and "['a', 'b']" are just specific instances of that type. That's why [] is not allowed in that context ;)

I can see the reasoning but it's still inconsistent. In java we still have the [] notation for the type. For example:

int[] myArray = new int[4];

or

public static void main(String[] args)


Where the array hinting and type syntax is the same as the creation syntax without the new keyword.