【php8上級/準上級試験】模擬問題解説 問題15.

class Hoge {
    public function f1() {
        echo __METHOD__, PHP_EOL;
        return $this;
    }

    public function f2() {
        echo __METHOD__, PHP_EOL;
        return null;
    }

    public function f3() {
        echo __METHOD__, PHP_EOL;
        return $this;
    }
}

$val = (new Hoge())?->f1()?->f2()?->f3();
var_dump($val);

Hoge::f1
Hoge::f2
NULL

var_dump( 2 == '2' );
var_dump( 0 == '0' );
var_dump( 2 == '2a' );
var_dump( 0 == '' );
var_dump( 0 == 'foo' );

bool(true)
bool(true)
bool(true)
bool(true)
bool(true)

bool(true)
bool(true)
bool(false)
bool(false)
bool(false)

class Hoge {
    final private function pFunc1() {
        echo __METHOD__, PHP_EOL;
    }
}

class Foo extends Hoge {
    private function pFunc1() {
        parent::pFunc1();
        echo __METHOD__, PHP_EOL;
    }

    public function callPri() {
        $this->pFunc1();
    }
}

(new Foo())->callPri();

PHP Fatal error: Cannot override final method Hoge::pFunc1() in …

Hoge::pFunc1
Foo::pFunc1

class Hoge {
}

var_dump( Hoge::class );
$obj = new Hoge();
var_dump( $obj::class );

PHP Fatal error:  Cannot use ::class with dynamic class name in ...

string(4) "Hoge"
string(4) "Hoge"