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0 Private
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public ; echo $this -> protected ; echo $this -> private ; } } $obj = new MyClass (); echo $obj -> public ; // Работает echo $obj -> protected ; // Неисправимая ошибка echo $obj -> private ; // Неисправимая ошибка $obj -> printHello (); // Выводит Public, Protected и Private /** * Определение MyClass2 */ class MyClass2 extends MyClass { // Мы можем переопределить общедоступные и защищённые свойства, но не закрытые public $public = 'Public2' ; protected $protected = 'Protected2' ; function printHello () { echo $this -> public ; echo $this -> protected ; echo $this -> private ; } } $obj2 = new MyClass2 (); echo $obj2 -> public ; // Работает echo $obj2 -> private ; // Неопределён echo $obj2 -> protected ; // Неисправимая ошибка $obj2 -> printHello (); // Выводит Public2, Protected2, Undefined ?>
MyPublic (); $this -> MyProtected (); $this -> MyPrivate (); } } $myclass = new MyClass ; $myclass -> MyPublic (); // Работает $myclass -> MyProtected (); // Неисправимая ошибка $myclass -> MyPrivate (); // Неисправимая ошибка $myclass -> Foo (); // Работает общедоступный, защищённый и закрытый /** * Определение MyClass2 */ class MyClass2 extends MyClass { // Это общедоступный метод function Foo2 () { $this -> MyPublic (); $this -> MyProtected (); $this -> MyPrivate (); // Неисправимая ошибка } } $myclass2 = new MyClass2 ; $myclass2 -> MyPublic (); // Работает $myclass2 -> Foo2 (); // Работает общедоступный и защищённый, закрытый не работает class 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 ?>
foo (); // Выводятся константы public, protected и private /** * Объявление класса MyClass2 */ class MyClass2 extends MyClass { // Публичный метод function foo2 () { echo self :: MY_PUBLIC ; echo self :: MY_PROTECTED ; echo self :: MY_PRIVATE ; // Неисправимая ошибка } } $myclass2 = new MyClass2 ; echo MyClass2 :: MY_PUBLIC ; // Работает $myclass2 -> foo2 (); // Выводятся константы public и protected, но не private ?>
foo = $foo ; } private function bar () { echo 'Доступ к закрытому методу.' ; } public function baz ( Test $other ) { // Мы можем изменить закрытое свойство: $other -> foo = 'привет' ; var_dump ( $other -> foo ); // Мы также можем вызвать закрытый метод: $other -> bar (); } } $test = new Test ( 'test' ); $test -> baz (new Test ( 'other' )); ?>
string(6) "привет"
Доступ к закрытому методу.
add a note
User Contributed Notes 26 notes
INSIDE CODE and OUTSIDE CODE label = 'Ink-Jet Tatoo Gun' ; $item -> price = 49.99 ; ?> Ok, that's simple enough... I got it inside and out. The big problem with this is that the Item class is COMPLETELY IGNORANT in the following ways: * It REQUIRES OUTSIDE CODE to do all the work AND to know what and how to do it -- huge mistake. * OUTSIDE CODE can cast Item properties to any other PHP types (booleans, integers, floats, strings, arrays, and objects etc.) -- another huge mistake. Note: we did it correctly above, but what if someone made an array for $price? FYI: PHP has no clue what we mean by an Item, especially by the terms of our class definition above. To PHP, our Item is something with two properties (mutable in every way) and that's it. As far as PHP is concerned, we can pack the entire set of Britannica Encyclopedias into the price slot. When that happens, we no longer have what we expect an Item to be. INSIDE CODE should keep the integrity of the object. For example, our class definition should keep $label a string and $price a float -- which means only strings can come IN and OUT of the class for label, and only floats can come IN and OUT of the class for price. label and $item->price, * by using the protected keyword. * 2. FORCE the use of public functions. * 3. ONLY strings are allowed IN & OUT of this class for $label * via the getLabel and setLabel functions. * 4. ONLY floats are allowed IN & OUT of this class for $price * via the getPrice and setPrice functions. */ protected $label = 'Unknown Item' ; // Rule 1 - protected. protected $price = 0.0 ; // Rule 1 - protected. public function getLabel () { // Rule 2 - public function. return $this -> label ; // Rule 3 - string OUT for $label. } public function getPrice () { // Rule 2 - public function. return $this -> price ; // Rule 4 - float OUT for $price. } public function setLabel ( $label ) // Rule 2 - public function. { /** * Make sure $label is a PHP string that can be used in a SORTING * alogorithm, NOT a boolean, number, array, or object that can't * properly sort -- AND to make sure that the getLabel() function * ALWAYS returns a genuine PHP string. * * Using a RegExp would improve this function, however, the main * point is the one made above. */ if( is_string ( $label )) { $this -> label = (string) $label ; // Rule 3 - string IN for $label. } } public function setPrice ( $price ) // Rule 2 - public function. { /** * Make sure $price is a PHP float so that it can be used in a * NUMERICAL CALCULATION. Do not accept boolean, string, array or * some other object that can't be included in a simple calculation. * This will ensure that the getPrice() function ALWAYS returns an * authentic, genuine, full-flavored PHP number and nothing but. * * Checking for positive values may improve this function, * however, the main point is the one made above. */ if( is_numeric ( $price )) { $this -> price = (float) $price ; // Rule 4 - float IN for $price. } } } ?> Now there is nothing OUTSIDE CODE can do to obscure the INSIDES of an Item. In other words, every instance of Item will always look and behave like any other Item complete with a label and a price, AND you can group them together and they will interact without disruption. Even though there is room for improvement, the basics are there, and PHP will not hassle you... which means you can keep your hair!
If you have problems with overriding private methods in extended classes, read this:)
The manual says that "Private limits visibility only to the class that defines the item". That means extended children classes do not see the private methods of parent class and vice versa also.
As a result, parents and children can have different implementations of the "same" private methods, depending on where you call them (e.g. parent or child class instance). Why? Because private methods are visible only for the class that defines them and the child class does not see the parent's private methods. If the child doesn't see the parent's private methods, the child can't override them. Scopes are different. In other words -- each class has a private set of private variables that no-one else has access to.
A sample demonstrating the percularities of private methods when extending classes:
overridden ();
}
private function overridden () {
echo 'base' ;
}
}
class child extends base {
private function overridden () {
echo 'child' ;
}
}
$test = new child ();
$test -> inherited ();
?>
Output will be "base".
If you want the inherited methods to use overridden functionality in extended classes but public sounds too loose, use protected. That's what it is for:)
A sample that works as intended:
overridden ();
}
protected function overridden () {
echo 'base' ;
}
}
class child extends base {
protected function overridden () {
echo 'child' ;
}
}
$test = new child ();
$test -> inherited ();
?>
Output will be "child".
Just a quick note that it's possible to declare visibility for multiple properties at the same time, by separating them by commas. eg:
A class A static public function can access to class A private function : foo (); } } $a = new A (); A :: bar ( $a ); ?> It's working.
1 . If the class member declared as public then it can be accessed everywhere. 2 . If the class members declared as protected then it can be accessed only within the class itself and by inheriting and parent classes. 3 .If the class members declared as private then it may only be accessed by the class that defines the member. tag_line . "" ; } } // SubClass class child extends pub { function show (){ echo $this -> tag_line ; } } // Object Declaration $obj = new child ; // A Computer Science Portal for Geeks! echo $obj -> tag_line . "" ; // A Computer Science Portal for Geeks! $obj -> display (); // A Computer Science Portal for Geeks! $obj -> show (); ?> x - $this -> y . "" ; } } // SubClass - Inherited Class class child extends pro { function mul () //Multiply Function { echo $sub = $this -> x * $this -> y ; } } $obj = new child ; $obj -> sub (); $obj -> mul (); ?> name ; } } // Object Declaration $obj = new child ; // Uncaught Error: Call to private method demo::show() $obj -> show (); //Undefined property: child::$name $obj -> display (); ?>
private , $this -> public \n" ; } } class B extends A { function __construct () { $this -> private = 2 ; $this -> public = 2 ; } function set () { $this -> private = 3 ; $this -> public = 3 ; } function get () { return parent :: get () . "B: $this -> private , $this -> public \n" ; } } $B = new B ; echo $B -> get (); echo $B -> set (); echo $B -> get (); ?> ?> Result is A: 1 , 2 B: 2 , 2 A: 1 , 3 B: 3 , 3 This is correct code and does not warn you to use any private. "$this->private" is only in A private. If you write it in class B it's a runtime declaration of the public variable "$this->private", and PHP doesn't even warn you that you create a variable in a class without declaration, because this is normal behavior.
Please note that protected methods are also available from sibling classes as long as the method is declared in the common parent. This may also be an abstract method. In the below example Bar knows about the existence of _test() in Foo because they inherited this method from the same parent. It does not matter that it was abstract in the parent. _test (); } } class Foo extends Base { protected function _test () { echo 'Foo' ; } } $bar = new Bar (); $bar -> TestFoo (); // result: Foo ?>
Beware: Visibility works on a per-class-base and does not prevent instances of the same class accessing each others properties! bar , "\n" ; } public function setBar ( $value ) { // Neccessary method, for $bar is invisible outside the class $this -> bar = $value ; } public function setForeignBar ( Foo $object , $value ) { // this does NOT violate visibility! $object -> bar = $value ; } } $a = new Foo (); $b = new Foo (); $a -> setBar ( 1 ); $b -> setBar ( 2 ); $a -> debugBar ( $b ); // 2 $b -> debugBar ( $a ); // 1 $a -> setForeignBar ( $b , 3 ); $b -> setForeignBar ( $a , 4 ); $a -> debugBar ( $b ); // 3 $b -> debugBar ( $a ); // 4 ?>
The code prints
test Object ( [public] => Public var [protected:protected] => protected var [private:test:private] => Private var )
Functions like print_r(), var_dump() and var_export() prints public, protected and private variables, but not the static variables.
if not overwritten, self::$foo in a subclass actually refers to parent's self::$foo tell_me (); // bar $first -> change_foo ( "restaurant" ); $second -> tell_me (); // restaurant ?>
Some Method Overriding rules : 1. In the overriding, the method names and arguments (arg’s) must be same. Example: class p { public function getName(){} } class c extends P{ public function getName(){} } 2. final methods can’t be overridden. 3. private methods never participate in the in the overriding because these methods are not visible in the child classes. Example: class a { private function my(){ print "parent:my"; } public function getmy(){ $this->my(); } } class b extends a{ private function my(){ print "base:my"; } } $x = new b(); $x->getmy(); // parent:my 4. While overriding decreasing access specifier is not allowed class a { public function my(){ print "parent:my"; } } class b extends a{ private function my(){ print "base:my"; } } //Fatal error: Access level to b::my() must be public (as in class a)
I have simplified the last method (Example #4) showing how to call private function outside the class. I think this is an idea of that example: bar (); } } $test =new Test (); $test -> baz (); $test -> bar (); ?>
This has already been noted here, but there was no clear example. Methods defined in a parent class can NOT access private methods defined in a class which inherits from them. They can access protected, though. Example: $method (); } } class ChildClass extends ParentClass { private function privateMethod () { echo "hi, i'm private" ; } protected function protectedMethod () { echo "hi, i'm protected" ; } } $object = new ChildClass (); $object -> execute ( 'protectedMethod' ); $object -> execute ( 'privateMethod' ); ?> Output: hi, i'm protected Fatal error: Call to private method ChildClass::privateMethod() from context 'ParentClass' in index.php on line 6 In an early approach this may seem unwanted behaviour but it actually makes sense. Private can only be accessed by the class which defines, neither parent nor children classes.
> Members declared protected can be accessed only within > the class itself and by inherited classes. Members declared > as private may only be accessed by the class that defines > the member. This is not strictly true. Code outside the object can get and set private and protected members: string(3) "foo" call_user_func (\ Closure :: bind ( function () use ( $sealed ) { $sealed -> value = 'BAZ' ; }, null , $sealed )); var_dump ( $sealed ); // private $value => string(3) "BAZ" ?> The magic lay in \Closure::bind, which allows an anonymous function to bind to a particular class scope. The documentation on \Closure::bind says: > If an object is given, the type of the object will be used > instead. This determines the visibility of protected and > private methods of the bound object. So, effectively, we're adding a run-time setter to $sealed, then calling that setter. This can be elaborated to generic functions that can force set and force get object members: { $property } = $value ; }, null , $object )); } function force_get ( $object , $property ) { return call_user_func (\ Closure :: bind ( function () use ( $object , $property ) { return $object ->{ $property }; }, null , $object )); } force_set ( $sealed , 'value' , 'quux' ); var_dump ( force_get ( $sealed , 'value' )); // 'quux' ?> You should probably not rely on this ability for production quality code, but having this ability for debugging and testing is handy.
I couldn't find this documented anywhere, but you can access protected and private member varaibles in different instance of the same class, just as you would expect i.e. prot = $a ; $this -> priv = $b ; } public function print_other ( A $other ) { echo $other -> prot ; echo $other -> priv ; } } class B extends A { } $a = new A ( "a_protected" , "a_private" ); $other_a = new A ( "other_a_protected" , "other_a_private" ); $b = new B ( "b_protected" , "ba_private" ); $other_a -> print_other ( $a ); //echoes a_protected and a_private $other_a -> print_other ( $b ); //echoes b_protected and ba_private $b -> print_other ( $a ); //echoes a_protected and a_private ?>
Print ( '000' ); echo $b -> PrintPrivate ( "000" ); //Fatal error: Uncaught Error: Call to private method BaseOne::PrintPrivate() from context... echo $b -> PrintProtected ( "000" ); //Fatal error: Uncaught Error: Call to protected method BaseOne::PrintProtected() from context...
Interestingly enough, PHP does very reasonable job in regards to interaction between classes and plain functions (even ones defined in the same file as the class)
bar (); // works
$test -> foo (); // works
}
}
function simple_function () {
$test = new Test ();
$test -> bar (); // does not work
$test -> foo (); // does not work
Test :: foobar ( $test ); // works
}
simple_function ();
?>
As far as it regards the properties of objects, visibility is, yes, as the examples show. Private, protected methods are not accessible via syntax $a->protectedVar, however their values are still (php 5.3.26) accessible through a number of other methods (serializing, converting to array, and nevertheless using the ReflectionClass methods). As it was pointed out and such as in the example below: bar3 ) . "\n" ; echo ( $obj -> bar2 ) . "\n" ; echo ( $obj -> bar ) . "\n" ; ?> It will output: PHP Version: 5.3.26 O:3:"Foo":3:{s:8:"Foobar";s:20:"value of private var ";s:7:"*bar2";s:22:"value of protected var";s:4:"bar3";s:19:"value of public var";} Foo Object ( [bar:Foo:private] => value of private var [bar2:protected] => value of protected var [bar3] => value of public var ) Array ( [Foobar] => value of private var [*bar2] => value of protected var [bar3] => value of public var ) value of public var While the last two lines, accessing directly the private and protected object properties (bar2 and bar), will throw out fatal errors like: PHP Fatal error: Cannot access private property Foo::$bar and PHP Fatal error: Cannot access protected property Foo::$bar2
Private or not private? I get baffled whenever I see this kind of an example. things = $things ; } public function getThing ( $obj ){ return $obj -> things ; } } class smallVessel { private $things = array(); public function setThing ( $things ){ $this -> things = $things ; } public function getThing ( $obj ){ return $obj -> things ; } } $basket = new vessel (); $bucket = new vessel (); $bowl = new smallVessel (); $basket -> setThing (array( 'wine' , 'water' , 'sugar' )); // returns the contents inside basket unexpectedly print_r ( $bucket -> getThing ( $basket )); // returns error, quite rightly so! print_r ( $bowl -> getThing ( $basket ));
access a protected property: foo = $afoo ; } } ?> if you get an instance of aa and need access to $foo: foo ; } } $aainstance = someexternalfunction (); $binstance =new b ; $aafoo = $binstance -> getFoo ( $aainstance ); ?>
Just wanted to share a trap for the unwary. Where there are several layers of object assignments, setting the bottom object's properties as private will prevent its exposure. However, if the bottom object has public properties, intermediate objects which are themselves set as private but are derived from the bottom object can inadvertently be exposed to updates. This follows logically from the reference model in php ( http://php.net/manual/en/language.oop5.references.php ), but can yield a result that is surprising until one gets the reference model. The following example demonstrates the phenomenon. // underlying class for offering database results to other objects // __construct method yields public results -- bottom object in example class database_result { public $column1; public function __construct() { // . . . database access . . . $this->column1 = 'foo'; } } // application dictionary accesses database and caches results // for application objects -- this is the second layer in the example class dictionary { private $reference_object; public function __construct (){ $this->reference_object = new database_result; } public function get_reference_object() { return ( $this->reference_object ); } } $dictionary = new dictionary; /* $dictionary->reference_object cannot be accessed directly * $dictionary->reference_object->column1 = 'foochanged'; * yields Fatal error: Cannot access private property dictionary::$reference_object in /var/www/html/index.php . . . */ $pointer_to_dictionary = $dictionary; /* * if assign $dictionary to new variable, the new variable is a pointer and its properties are still private * $pointer_to_dictionary->reference_object->column1 = 'foochanged'; * Fatal error: Cannot access private property dictionary::$reference_object in /var/www/html/index.php . . . * $pointer_to_dictionary = $dictionary->reference_object; * Fatal error: Cannot access private property dictionary::$reference_object in /var/www/html/index.php . . . */ // now set up a client class that will use a working copy of the dictionary -- this is the third layer in the example class dictionary_user { private $pointer_to_dictionary; public function __construct () { global $dictionary; // $this->pointer_to_dictionary = $dictionary->reference_object; // Fatal error: Cannot access private property dictionary::$reference_object in /var/www/html/index.php . . . // still cannot directly access dictionary properties even in this context, except through getter $this->pointer_to_dictionary = $dictionary->get_reference_object(); } // however, can now operate on dictionary through the pointer public function set_pointer_to_dictionary ( $value ) { $this->pointer_to_dictionary->column1 = $value; } public function get_pointer_to_reference_object(){ return ($this->pointer_to_dictionary); } } $dictionary_user = new dictionary_user; $dictionary_user->set_pointer_to_dictionary ( 'foochanged' ); echo (''); var_dump ( $dictionary_user->get_pointer_to_reference_object()); echo ''; // object(database_result)#2 (1) { ["column1"]=> string(10) "foochanged" } -- of course, the user object is changed var_dump ( $dictionary->get_reference_object() ); // object(database_result)#2 (1) { ["column1"]=> string(10) "foochanged" } -- however, the private dictionary object is also now corrupted! // Note: If the underlying database result object $column1 as private, this will cause set_pointer_to_dictionary to generate the usual fatal error // but making the bottom object private may defeat its purpose of exposing results.
If you miss the "package" keyword in PHP in order to allow access between certain classes without their members being public, you can utilize the fact, that in PHP the protected keyword allows access to both subclasses and superclasses. So you can use this simple pattern: $pName ; } protected function invokeMethod ( $pObj , $pName , $pArgs ) { return call_user_func_array (array( $pObj , $pName ), $pArgs ); } } ?> The classes that should be privileged to each other simply extend this dispatcher: name = $pName ; $this -> phoneNumbers = array(); } public function addNumber ( PhoneNumber $pNumber , $pLabel ) { $this -> phoneNumbers [ $pLabel ] = $pNumber ; // this does not work, because "owner" is protected: // $pNumber->owner = $this; // instead, we get a reference from the dispatcher: $p =& $this -> accessProperty ( $pNumber , "owner" ); // ... and change that: $p = $this ; } public function call ( $pLabel ) { // this does not work since "call" is protected: // $this->phoneNumbers[$pLabel]->call(); // instead, we dispatch the call request: $this -> invokeMethod ( $this -> phoneNumbers [ $pLabel ], "call" , array()); } } class PhoneNumber extends Dispatcher { private $countryCode ; private $areaCode ; private $number ; protected $owner ; public function __construct ( $pCountryCode , $pAreaCode , $pNumber ) { $this -> countryCode = $pCountryCode ; $this -> areaCode = $pAreaCode ; $this -> number = $pNumber ; } protected function call () { echo( "calling " . $this -> countryCode . "-" . $this -> areaCode . "-" . $this -> number . "\n" ); } } $person = new Person ( "John Doe" ); $number1 = new PhoneNumber ( 12 , 345 , 67890 ); $number2 = new PhoneNumber ( 34 , 5678 , 90123 ); $person -> addNumber ( $number1 , "home" ); $person -> addNumber ( $number2 , "office" ); $person -> call ( "home" ); ?> Without this pattern you would have to make $owner and call() public in PhoneNumber. Best regards,
After having the how explained, many people will still be left wondering about the why. How should the different kinds of visibility be used in practice? Some kind of labelling for the public and private parts of an interface is certainly necessary. We need to be clear which methods will be part of the public interface and which are only used internally . In older versions of php notionally-private functions were prefixed with an underscore - a much simpler and more elegant solution to the labelling problem. "Protected" adds clutter which affects readability. It adds a lot of unnecessary typing to what is already a keyboard-intensive job. As for enforcement.. no-one ever got mixed up about public/private so long as they were clearly labelled. As such, "protected" is an attempt to solve a problem which simply did not exist. Private is even worse. It specifically encourages bad object-oriented code with the use of inheritance in places where you should be thinking about separate, co-operating objects. A feeling that classes which inherit from each other need to hide some of their bits from each other is a sure sign that you need to break the code up into separate objects. This is exactly what encapsulation is for. It doesn't make any sense to try to encapsulate bits inside an inheritance tree. Classes which extend other classes must always be free to override whatever it is they need to override in their parent classes. In short, use protected if you must, do not use private at all. Do not try to squeeze too much new functionality into an inheritance tree: create networks of co-operating objects with clearly-defined responsibilities instead. It's a real shame that php took the decision to implement private and protected. They add nothing to our ability to write good quality OO code; they simply make that code more difficult to write and to understand. Clarity and simplicity are incredibly important in programming but now both php programmers and php developers are stuck with these unnecessary layers of complexity.
Re: wbcarts at juno dot com Expected, since it comes down to PHP's lack of type enforcement. Classes preserve structure, but doesn't natively enforce scalar property types, as per PHP's variables. 'It REQUIRES OUTSIDE CODE to do all the work...' No, as you indicate, to mitigate this, make variables private and use protected/public 'set' and 'get' types of methods to manipulate their values. However, the 'set' functions would also need to enforce type and report errors if not of the correct type. Of course, the code that uses classes should be designed to either: a. Provide only the correct types of values. b. Handle the errors reported. c. Encapsulate use of the class with try-catch blocks. Note that c. is what sloppy code feeding mistyped values to the class would have to do if type were strictly enforced. Fortunately, as of 7.0, type can be specified for scalar function/method parameters, but would need try-catch blocks to handle mismatches from inside the class, rather than using the 'is' functions. All of this is part of proper design and defensive programming.
When overriding a private method with a more visible child method, the parent method may be called instead. foo (); } } class Child extends Parent { public function foo () { echo "Child Foo\n" ; } } $bar = new Child (); $bar -> call_foo (); $bar -> foo (); ?> will output: Parent Foo Child Foo
I want to merge notes from different comments about visibility of class members from parent class / sibling class point of view because visibility rules are similar. Here are main points: 1. Methods declared in parent class can access some child class members. 2. Class can access some sibling class members using methods declared in common parent. NB: only inherited not-overridden parent method could be used, if you override it in current class you have to call parent method statically to get access to sibling members. You can see list of members that could be accessed via these methods below: - inherited protected / private property – OK; - inherited protected / private method without overriding – OK; - inherited protected method with overriding – OK; - inherited private method with overriding – FAIL, original parent method will be called; - own protected property / method – OK; - own private property / method – FAIL, critical error.
Область видимости свойства, метода или константы (начиная c PHP 7.1.0) может быть определена путём
использования следующих ключевых слов в объявлении: public ,
protected или private . Доступ к свойствам
и методам класса, объявленным как public (общедоступный), разрешён отовсюду.
Модификатор protected (защищённый) разрешает доступ самому классу, наследующим его классам и родительским классам.
Модификатор private (закрытый) ограничивает область видимости так, что только класс,
где объявлен сам элемент, имеет к нему доступ.
Свойства класса должны быть определены через модификаторы public, private
или protected. Если же свойство определено с помощью var ,
то оно будет объявлено общедоступным свойством.
Пример #1 Объявление свойства класса
Методы класса должны быть определены через модификаторы public, private,
или protected. Методы, где определение модификатора отсутствует,
определяются как public.
Начиная с PHP 7.1.0, константы класса могут быть определены как public, private или
protected. Константы, объявленные без указания области видимости,
определяются как public.
Пример #3 Объявление констант, начиная с PHP 7.1.0
Объекты, которые имеют общий тип (наследуются от одного класса), имеют доступ к элементам с модификаторами
private и protected друг друга, даже если не являются одним и тем же экземпляром.
Это объясняется тем, что реализация видимости элементов известна внутри этих объектов.
Пример #4 Доступ к элементам с модификатором private из объектов одного типа
Результат выполнения данного примера:
Private network - Wikipedia
PHP: Область видимости - Manual
Swift 3. 0 : Private vs. Fileprivate | by Felicity Johnson | Medium
GitHub - licensezero/licensezero- private -license: standard form private ...
swift3 - Difference between fileprivate and private ... - Stack Overflow
According to Apple’s documentation, “Private access restricts the use of an entity to the enclosing declaration.” Private access is the most restrictive access level. Basically this just means that you are not able to access the private type/func/property outside of the scope in which the private entity was defined.
In the example below, since var visibleButton and f u nc getAge() were both defined within the PrivatePerson class, we are able to access those funcs within the entire scope of the PrivatePerson class. However, we are NOT able to access those entities within the PrivatePerson extension since the extension is NOT within the scope of the class in which the private entities were defined.
Given what you know from above, can you explain why I made the handleTapGesture func private?
Since the handleTapGesture func is a helper method and will only be called on by the configButtons() func in the extension, I decided to limit the access of the func solely to the extension. If I tried to call on the handleTapGesture func within the class’s definition, I would receive an “inaccessible due to ‘private’ protection level” error.
According to Apple’s documentation, “Fileprivate access restricts the use of an entity to its own defining source file.” If you are familiar with Swift 2.0, fileprivate is the equivalent of Swift 2.0’s private.
The main difference between fileprivate and private is evidenced below. Fileprivate entities can be accessed within the entire file. In the example below, even though var invisibleButton and getName() were defined in the FileprivatePerson class, we can still access them within the FileprivatePerson extension.
You might be wondering why you have never had to define an entity as private/fileprivate and you have never received any warnings. This is because Swift defaults to “internal,” meaning the entity (type/func/property etc.) is accessible to the entire app/framework that includes the entity’s definition. Defining an entity as private/fileprivate is just going one step further in terms of your thoughtfulness about the code you are writing. Happy coding! 🤓
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