奋斗足迹|崔玉松

The Scope Resolution Operator (also called Paamayim Nekudotayim) or in simpler terms, the double colon, is a token that allows access to static, constant, and overridden members or methods of a class.

When referencing these items from outside the class definition, use the name of the class.

Paamayim Nekudotayim would, at first, seem like a strange choice for naming a double-colon. However, while writing the Zend Engine 0.5 (which powers PHP 3), that’s what the Zend team decided to call it. It actually does mean double-colon – in Hebrew!

class MyClass {
const CONST_VALUE = 'A constant value';
}

echo MyClass::CONST_VALUE;
?>

Two special keywords self and parent are used to access members or methods from inside the class definition. Calling a parent’s method

class MyClass
{
protected function myFunc() {
echo "MyClass::myFunc()n";
}
}

class OtherClass extends MyClass
{
// Override parent's definition
public function myFunc()
{
// But still call the parent function
parent::myFunc();
echo "OtherClass::myFunc()n";
}
}

$class = new OtherClass();
$class->myFunc();
?>

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.

A note about private members, the doc says “Private limits visibility only to the class that defines the item” this says that the following code works as espected:

class A {
private $_myPrivate="private";

public function showPrivate()
{
echo $this->_myPrivate.”n”;
}
}

class B extends A {
public function show()
{
$this->showPrivate();
}
}

$obj=new B();
$obj->show(); // shows “privaten”;
?>

this works cause A::showPrivate() is defined in the same class as $_myPrivate and has access to it.

You may define grouped variables separated by commas if they have the same visibility. This works for both initialized and uninitialized variables.

class Window
{
public $x = 0, $y = 100, $width = 1024, $height = 768;
}
?>

Handy if no comments are required or you’re inside a DocBlock.

The term hacking has a bad reputation in the press. They use it to refer to someone who breaks into systems or wreaks havoc with computers as their weapon.

Among people who write code, though, the term hack refers to a “quick-and-dirty” solution to a problem, or a clever way to get something done.

And the term hacker is taken very much as a compliment, referring to someone as being creative, having the technical chops to get things done.

The Hacks series is an attempt to reclaim the word, document the good ways people are hacking, and pass the hacker ethic of creative participation on to the uninitiated.

Seeing how others approach systems and problems is often the quickest way to learn about a new technology.