Visibility

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- Visibility

## Visibility

The visibility of a property, a method or (as of PHP 7.1.0) a constant can be defined by prefixing the declaration with the keywords `public`, `protected` or `private`. Class members declared public can be accessed everywhere. Members declared protected can be accessed only within the class itself and by inheriting and parent classes. Members declared as private may only be accessed by the class that defines the member.

### Property Visibility

Class properties may be defined as public, private, or protected. Properties declared without any explicit visibility keyword are defined as public.

Example #1 Property declaration

    <?php/** * Define MyClass */class MyClass{    public $public = 'Public';    protected $protected = 'Protected';    private $private = 'Private';    function printHello()    {        echo $this->public;        echo $this->protected;        echo $this->private;    }}$obj = new MyClass();echo $obj->public; // Worksecho $obj->protected; // Fatal Errorecho $obj->private; // Fatal Error$obj->printHello(); // Shows Public, Protected and Private/** * Define MyClass2 */class MyClass2 extends MyClass{    // We can redeclare the public and protected properties, but not private    public $public = 'Public2';    protected $protected = 'Protected2';    function printHello()    {        echo $this->public;        echo $this->protected;        echo $this->private;    }}$obj2 = new MyClass2();echo $obj2->public; // Worksecho $obj2->protected; // Fatal Errorecho $obj2->private; // Undefined$obj2->printHello(); // Shows Public2, Protected2, Undefined?>

### Method Visibility

Class methods may be defined as public, private, or protected. Methods declared without any explicit visibility keyword are defined as public.

Example #2 Method Declaration

    <?php/** * Define MyClass */class MyClass{    // Declare a public constructor    public function __construct() { }    // Declare a public method    public function MyPublic() { }    // Declare a protected method    protected function MyProtected() { }    // Declare a private method    private function MyPrivate() { }    // This is public    function Foo()    {        $this->MyPublic();        $this->MyProtected();        $this->MyPrivate();    }}$myclass = new MyClass;$myclass->MyPublic(); // Works$myclass->MyProtected(); // Fatal Error$myclass->MyPrivate(); // Fatal Error$myclass->Foo(); // Public, Protected and Private work/** * Define MyClass2 */class MyClass2 extends MyClass{    // This is public    function Foo2()    {        $this->MyPublic();        $this->MyProtected();        $this->MyPrivate(); // Fatal Error    }}$myclass2 = new MyClass2;$myclass2->MyPublic(); // Works$myclass2->Foo2(); // Public and Protected work, not Privateclass Bar {    public function test() {        $this->testPrivate();        $this->testPublic();    }    public function testPublic() {        echo "Bar::testPublic\n";    }        private function testPrivate() {        echo "Bar::testPrivate\n";    }}class Foo extends Bar {    public function testPublic() {        echo "Foo::testPublic\n";    }        private function testPrivate() {        echo "Foo::testPrivate\n";    }}$myFoo = new Foo();$myFoo->test(); // Bar::testPrivate                 // Foo::testPublic?>

### Constant Visibility

As of PHP 7.1.0, class constants may be defined as public, private, or protected. Constants declared without any explicit visibility keyword are defined as public.

Example #3 Constant Declaration as of PHP 7.1.0

    <?php/** * Define MyClass */class MyClass{    // Declare a public constant    public const MY_PUBLIC = 'public';    // Declare a protected constant    protected const MY_PROTECTED = 'protected';    // Declare a private constant    private const MY_PRIVATE = 'private';    public function foo()    {        echo self::MY_PUBLIC;        echo self::MY_PROTECTED;        echo self::MY_PRIVATE;    }}$myclass = new MyClass();MyClass::MY_PUBLIC; // WorksMyClass::MY_PROTECTED; // Fatal ErrorMyClass::MY_PRIVATE; // Fatal Error$myclass->foo(); // Public, Protected and Private work/** * Define MyClass2 */class MyClass2 extends MyClass{    // This is public    function foo2()    {        echo self::MY_PUBLIC;        echo self::MY_PROTECTED;        echo self::MY_PRIVATE; // Fatal Error    }}$myclass2 = new MyClass2;echo MyClass2::MY_PUBLIC; // Works$myclass2->foo2(); // Public and Protected work, not Private?>

### Visibility from other objects

Objects of the same type will have access to each others private and protected members even though they are not the same instances. This is because the implementation specific details are already known when inside those objects.

Example #4 Accessing private members of the same object type

    <?phpclass Test{    private $foo;    public function __construct($foo)    {        $this->foo = $foo;    }    private function bar()    {        echo 'Accessed the private method.';    }    public function baz(Test $other)    {        // We can change the private property:        $other->foo = 'hello';        var_dump($other->foo);        // We can also call the private method:        $other->bar();    }}$test = new Test('test');$test->baz(new Test('other'));?>

The above example will output:

    string(5) "hello"
    Accessed the private method.