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If you are new to PHP or just need to refresh your skills, this is the place to start. This series of tutorials will give you the basic knowledge you will need to create a simple PHP website.

PHP is a reflective programming language originally designed for producing dynamic web pages.[1] PHP is used mainly in server-side scripting, but can be used from a command line interface or in standalone graphical applications. Textual User Interfaces can also be created using ncurses.

PHP Manual
PrevChapter 19. Classes and Objects (PHP 5)Next

Visibility

The visibility of a property or method can be defined by prefixing the declaration with the keywords: public, protected or private. Public declared items can be accessed everywhere. Protected limits access to inherited and parent classes (and to the class that defines the item). Private limits visibility only to the class that defines the item.

Members Visibility

Class members must be defined with public, private, or protected.

Example 19-10. Member 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; // Works
echo $obj->protected; // Fatal Error
echo $obj->private; // Fatal Error
$obj->printHello(); // Shows Public, Protected and Private


/**
* Define MyClass2
*/
class MyClass2 extends MyClass
{
    
// We can redeclare the public and protected method, but not private
    
protected $protected = 'Protected2';

    function
printHello()
    {
        echo
$this->public;
        echo
$this->protected;
        echo
$this->private;
    }
}

$obj2 = new MyClass2();
echo
$obj->public; // Works
echo $obj2->private; // Undefined
echo $obj2->protected; // Fatal Error
$obj2->printHello(); // Shows Public, Protected2, not Private

?>

Note: The PHP 4 method of declaring a variable with the var keyword is still supported for compatibility reasons (as a synonym for the public keyword). In PHP 5 before 5.1.3, its usage would generate an E_STRICT warning.

Method Visibility

Class methods must be defined with public, private, or protected. Methods without any declaration are defined as public.

Example 19-11. Method Declaration

<?php
/**
* Define MyClass
*/
class MyClass
{
    
// Contructors must be public
    
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 Private
?>

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PHP is a widely-used general-purpose scripting language that is especially suited for Web development and can be embedded into HTML. If you are new to PHP and want to get some idea of how it works, try the introductory tutorial. After that, check out the online manual, and the example archive sites and some of the other resources available in the links section.