PHP8.1, 交差型って何？ なんだ、すべてを満たす型ってことか。

<?php

interface ParentTest{};
interface Child1 extends ParentTest{};
interface Child2 extends ParentTest{};
interface Child_1_1 extends Child1{};
interface Child_1_2 extends Child1{};
interface Child_2_1 extends Child2{};
interface Child_2_2 extends Child2{};

function test(Child_1_1&Child_1_2&Child_2_1 $types)
{
    return;
}

class Test implements Child_1_1, Child_1_2, Child_2_1{};
test(new Test());
echo 'program end' . PHP_EOL;

program end

class Test implements ParentTest{};
test(new Test());

PHP Fatal error:  Uncaught TypeError: test(): Argument #1 ($types) must be of type Child_1_1&Child_1_2&Child_2_1, Test given, called in /home/vagrant/php-test.php on line 17 and defined in /home/vagrant/php-test.php:11
Stack trace:
#0 /home/vagrant/php-test.php(17): test()
#1 {main}
  thrown in /home/vagrant/php-test.php on line 11

class Test implements Child1, Child2{};
test(new Test());

PHP Fatal error:  Uncaught TypeError: test(): Argument #1 ($types) must be of type Child_1_1&Child_1_2&Child_2_1, Test given, called in /home/vagrant/php-test.php on line 17 and defined in /home/vagrant/php-test.php:11
Stack trace:
#0 /home/vagrant/php-test.php(17): test()
#1 {main}
  thrown in /home/vagrant/php-test.php on line 11

class Test implements Child_1_1, Child_2_1{};
test(new Test());

PHP Fatal error:  Uncaught TypeError: test(): Argument #1 ($types) must be of type Child_1_1&Child_1_2&Child_2_1, Test given, called in /home/vagrant/php-test.php on line 17 and defined in /home/vagrant/php-test.php:11
Stack trace:
#0 /home/vagrant/php-test.php(17): test()
#1 {main}
  thrown in /home/vagrant/php-test.php on line 11

/**
 * PHP7以前
 */
function test(object $types)
{
    if (!$types instanceof Child_1_1 && !$types instanceof Child_1_2 && !$types instanceof Child_2_1) {
        throw new TypeError();
    }
    return;
}

function test(Child1&Child_2_1 $types)
{
    return;
}

class Test1 implements Child_1_1, Child_1_2, Child_2_1{};
class Test2 implements Child_1_1, Child_2_1{}; <--- 余計
class Test3 implements Child_1_2, Child_2_1{}; <--- 余計
class Test4 implements Child1, Child_2_1{};    <--- 余計
test(new Test1());
test(new Test2());
test(new Test3());
test(new Test4());
echo 'program end' . PHP_EOL;

program end

function test(Child_1_1|Child_1_2|Child_2_1 $types)
{
    return;
}