Thủ Thuật Hướng dẫn How to access private members of a class in php Mới Nhất
Hoàng Tiến Dũng đang tìm kiếm từ khóa How to access private members of a class in php được Update vào lúc : 2022-09-26 07:42:09 . Với phương châm chia sẻ Thủ Thuật Hướng dẫn trong nội dung bài viết một cách Chi Tiết Mới Nhất. Nếu sau khi Read Post vẫn ko hiểu thì hoàn toàn có thể lại Comment ở cuối bài để Tác giả lý giải và hướng dẫn lại nha.I have derived a class from Exception, basically like so:
Nội dung chính- Property VisibilityMethod VisibilityConstant VisibilityVisibility from other objectsHow can I access private property of a class in PHP?How can I access private variable from another class in PHP?How can I access private function in PHP?How do you access private members of a class in another class?
Then, I derived from MyException like so:
class SpecialException extends MyException private $_type = "superspecial";If I throw new SpecialException("bla") from a function, catch it, and go echo $e, then the __toString function should load a template, display that, and then not actually return anything to echo.
This is basically what's in the template file
message; ?>
in my mind, this should definitely work. However, I get the following error when an exception is thrown and I try to display it:
Fatal error: Cannot access private property SpecialException::$_type in C:pathtoexceptions.php on line 74
Can anyone explain why I am breaking the rules here? Am I doing something horribly witty with this code? Is there a much more idiomatic way to handle this situation? The point of the $_type variable is (as shown) that I want a different div class to be used depending on the type of exception caught.
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 thành viên.
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
/**
* 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; // Works
echo $obj->protected; // Fatal Error
echo $obj->private; // Fatal Error
$obj->printHello(); // Shows Public, Protected and Private
/**
* Define MyClass2
*/
// 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; // Works
echo $obj2->protected; // Fatal Error
echo $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
/**
* 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
*/
// 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::testPublicn";
private function
testPrivate()echo "Bar::testPrivaten";
class
Foo extends Barpublic function testPublic()
echo "Foo::testPublicn";
private function
testPrivate()echo "Foo::testPrivaten";
$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
/**
* 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; // Works
MyClass::MY_PROTECTED; // Fatal Error
MyClass::MY_PRIVATE; // Fatal Error
$myclass->foo(); // Public, Protected and Private work
/**
* Define MyClass2
*/
// 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
class 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.wbcarts juno dot com ¶
10 years ago
INSIDE CODE and OUTSIDE CODE
/**
* This is INSIDE CODE because it is written INSIDE the class.
*/
public $label;
public $price;
/**
* This is OUTSIDE CODE because it is written OUTSIDE the class.
*/
$item = new Item();
$item->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.
/**
* Here's the new INSIDE CODE and the Rules to follow:
*
* 1. STOP ACCESS to properties via $item->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!
what ever dot com ¶
13 years ago
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:
abstract class base
public function inherited()
$this->overridden();
private function overridden()
echo 'base';
class
child extends baseprivate 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:
abstract class base
public function inherited()
$this->overridden();
protected function overridden()
echo 'base';
class
child extends baseprotected function overridden()
echo 'child';
$test = new child();
$test->inherited();
?>
Output will be "child".
pgl yoyo dot org ¶
7 years ago
Just a quick note that it's possible to declare visibility for multiple properties the same time, by separating them by commas.
eg:
class a
protected $a, $b;
public
$c, $d;private
$e, $f;?>
stephane harobed dot org ¶
16 years ago
A class A static public function can access to class A private function :
class A
private function foo()
print("bar");
static public function
bar($a)$a->foo();
$a = new A();A::bar($a);
?>
It's working.
alexaulbach mayflower dot de ¶
9 years ago
error_reporting
(E_ALL | E_STRICT | E_ERROR | E_WARNING | E_PARSE | E_COMPILE_ERROR);class
Aprivate $private = 1;
public $public = 1;
function
get()return "A: $this->private , $this->publicn";
class
B extends Afunction
__construct()$this->private = 2;
$this->public = 2;
function
set()$this->private = 3;
$this->public = 3;
function
get()return parent::get() . "B: $this->private , $this->publicn";
$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.
r dot wilczek web-appz dot de ¶
16 years ago
Beware: Visibility works on a per-class-base and does not prevent instances of the same class accessing each others properties!
class Foo
private $bar;
public function
debugBar(Foo $object)// this does NOT violate visibility although $bar is private
echo $object->bar, "n";
public function
setBar($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
?>
Marce! ¶
13 years ago
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.
abstract class Base
abstract protected function _test();
class
Bar extends Baseprotected function
_test()public function
TestFoo()$c = new Foo();
$c->_test();
class
Foo extends Baseprotected function _test()
echo 'Foo';
$bar = new Bar();
$bar->TestFoo(); // result: Foo
?>
imran phptrack dot com ¶
13 years ago
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)
tushar dot khan0122 gmail dot com ¶
3 years ago
1 . If the class thành viên 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 thành viên.
class pub
public $tag_line = "A Computer Science Portal for Geeks!";
function display()
echo $this->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();
?>
class pro
protected $x = 500;
protected $y = 500; // Subtraction Function
function sub()
echo $sum=$this->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();
?>
class demo
private $name="A Computer Science Portal for Geeks!";
private function
show()echo "This is private method of base class";
// Sub Class
class child extends demo
function display()
echo $this->name;
// Object Declaration
$obj= new child; // Uncaught Error: Call to private method demo::show()
$obj->show(); //Undefined property: child::$name
$obj->display();
?>
IgelHaut ¶
10 years ago
class test
public $public = 'Public var';
protected $protected = 'protected var';
private $private = 'Private var';
public static
$static_public = 'Public static var';protected static $static_protected = 'protected static var';
private static $static_private = 'Private static var';
$class = new test;
print_r($class);
?>
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.
omega 2093 dot es ¶
10 years ago
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:
public function
execute($method)$this->$method();
class
ChildClass extends ParentClassprivate function
privateMethod()echo "hi, i'm private";
protected function
protectedMethod()echo "hi, i'm protected";
$object = new ChildClass();$object->execute('protectedMethod');$object->execute('privateMethod');?>
Output:
hi, i'm protected
Fatal error: Call to private method ChildClass::privateMethod() from context 'ParentClass' in index.php on line 6
In an early approach this may seem unwanted behaviour but it actually makes sense. Private can only be accessed by the class which defines, neither parent nor children classes.
jc dot flash gmail dot com ¶
10 years ago
if not overwritten, self::$foo in a subclass actually refers to parent's self::$foo
class one
protected static $foo = "bar";
public function change_foo($value)
self::$foo = $value;
class
two extends onepublic function tell_me()
echo self::$foo;
$first = new one;
$second = new two;$second->tell_me(); // bar
$first->change_foo("restaurant");
$second->tell_me(); // restaurant
?>
bishop php dot net ¶
5 years ago
> 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 thành viên.
This is not strictly true. Code outside the object can get and set private and protected members:
class Sealed private $value = 'foo'; $sealed = new Sealed;
var_dump($sealed); // private $value => string(3) "foo"call_user_func(Closure::bind(
function () use ($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 $sealed, then calling that setter. This can be elaborated to generic functions that can force set and force get object members:
function force_set($object, $property, $value)
call_user_func(Closure::bind(
function () use ($object, $property, $value)
$object->$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.
Joshua Watt ¶
15 years ago
I couldn't find this documented anywhere, but you can access protected and private thành viên varaibles in different instance of the same class, just as you would expect
i.e.
class A
protected $prot;
private $priv;
public function
__construct($a, $b)$this->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
?>
kostya eltexsoft dot com ¶
1 year ago
I see we can redeclare private properties into child class
class A
private int $private_prop = 4;
protected int $protected_prop = 8;
class
B extends Aprivate int $private_prop = 7; // we can redeclare private property!!!
public function printAll()
echo $this->private_prop;
echo $this->protected_prop;
$b = new B;
$b->printAll(); // show 78
}
?>
Vytautas ¶
2 years ago
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:
class Test
private $foo;
private function
bar()echo 'Accessed the private method.';
public function
baz()// Calling the private method:
$this->bar();
$test=new Test();
$test->baz();
$test->bar();
?>
andrei leapingbytes dot net ¶
9 years ago
Interestingly enough, PHP does very reasonable job in regards to interaction between classes and plain functions (even ones defined in the same file as the class)
private function foo()
echo "Foo" . PHP_EOL;
protected function bar()
echo "bar" . PHP_EOL;
static function
foobar($test)$test->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();
?>
thcdesigning gmail dot com ¶
8 years ago
Private or not private?
I get baffled whenever I see this kind of an example.
private $things = array();
public function
setThing($things)$this->things = $things;
public function
getThing($obj)return $obj->things;
class
smallVesselprivate $things = array();
public function
setThing($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));
aluciffer hotmail dot com ¶
9 years ago
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:
class
Fooprivate $bar = "value of private var";
protected $bar2 = "value of protected var";
public $bar3 = "value of public var";
$obj = new Foo;
echo
serialize($obj) . "n";print_r($obj);print_r((array)$obj);echo (
$obj->bar3) . "n";echo ($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::$bar2
tvitcom yandex dot ru ¶
2 years ago
//PHP Version 7.4.5 (compiled, as mod_cgi)class BaseOne
public function Print($a)
return $a . '123';
private function
PrintPrivate($a)return $a . '123';
protected function
PrintProtected($a)return $a . '123';
class
BaseTwo extends BaseOne $b = new BaseTwo();echo
$b->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...
Patanjali ¶
2 years ago
Re: wbcarts 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.
php stage-slash-solutions dot com ¶
11 years ago
access a protected property:
protected $foo;
class
aa extends afunction setFoo($afoo)
$this->foo = $afoo;
?>
if you get an instance of aa and need access to $foo:
class b extends a
function getFoo($ainstance)
return $ainstance->foo;
$aainstance=someexternalfunction();
$binstance=new b;
$aafoo=$binstance->getFoo($aainstance);
?>
a dot schaffhirt sedna-soft dot de ¶
13 years ago
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:
abstract class Dispatcher
protected function &accessProperty (self $pObj, $pName)
return $pObj->$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:
class Person extends Dispatcher
private $name;
protected $phoneNumbers;
public function
__construct ($pName)$this->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 Dispatcherprivate $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 $owner and call() public in PhoneNumber.
Best regards,
benjam ¶
2 years ago
When overriding a private method with a more visible child method, the parent method may be called instead.
private function foo()
echo "Parent Foon";
public function
call_foo()$this->foo();
class
Child extends Parentpublic function foo()
echo "Child Foon";
$bar = new Child();
$bar->call_foo();
$bar->foo();?>
will output:
Parent Foo
Child Foo
willbrownsberger gmail dot com ¶
7 years ago
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 ( ://php/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.
noel darlow ¶
6 years ago
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 không lấy phí to override whatever it is they need to override in their parent classes.
In short, use protected if you must, do not use private 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.
gried NOSPAM dot nsys dot by ¶
6 years ago
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.
How can I access private property of a class in PHP?
Way to Access Private Property or Method In PHP. class Foo private function privateMethod() return 'howdy'; $foo = new Foo; $foo->privateMethod(); ... . $reflectionMethod = new ReflectionMethod('Foo', 'privateMethod'); $reflectionMethod->setAccessible(true); echo $reflectionMethod->invoke(new Foo);.How can I access private variable from another class in PHP?
By using Public Method We can access a private variable in a different class by putting that variable with in a Public method and calling that method from another class by creating object of that class.How can I access private function in PHP?
php //Accessing private method in php with parameter class Foo private function validateCardNumber($number) echo $number; $method = new ReflectionMethod('Foo', 'validateCardNumber'); $method->setAccessible(true); echo $method->invoke(new Foo(), '1234-1234-1234'); ?>How do you access private members of a class in another class?
Only the thành viên functions or the friend functions are allowed to access the private data members of a class. We can access private method in other class using the virtual function, A virtual function is a thành viên function which is declared within a base class and is re-defined (Overridden) by a derived class. Tải thêm tài liệu liên quan đến nội dung bài viết How to access private members of a class in php programming php PHP method scope PHP protected static