PHP Classes and Objects
Introduction
Classes and Objects are used to to make your code more efficient and less repetitive by grouping similar tasks.
A class is used to define the actions and data structure used to build objects. The objects are then built using this predefined structure.
Syntax
class <ClassName> [ extends <ParentClassName> ] [ implements <Interface1> [, <Interface2>, ... ] { }// Class declarationinterface <InterfaceName> [ extends <ParentInterface1> [, <ParentInterface2>, ...] ] { }// Interface declarationuse <Trait1> [, <Trait2>, ...]; // Use traits[ public | protected | private ] [ static ] $<varName>;// Attribute declarationconst <CONST_NAME>;// Constant declaration[ public | protected | private ] [ static ] function <methodName>([args...]) { }// Method declaration
Remarks
Classes and Interface components
Classes may have properties, constants and methods.
- Properties hold variables in the scope of the object. They may be initialized on declaration, but only if they contain a primitive value.
- Constants must be initialized on declaration and can only contain a primitive value. Constant values are fixed at compile time and may not be assigned at run time.
- Methods must have a body, even an empty one, unless the method is declared abstract.
class Foo {
private $foo = 'foo'; // OK
private $baz = array(); // OK
private $bar = new Bar(); // Error!
}
Interfaces cannot have properties, but may have constants and methods.
- Interface constants must be initialized on declaration and can only contain a primitive value. Constant values are fixed at compile time and may not be assigned at run time.
- Interface methods have no body.
interface FooBar {
const FOO_VALUE = 'bla';
public function doAnything();
}
