object-oriented Programming in PHP: Ways to develop large PHP projects (II.) (reproduced)

Programming | object | object-oriented programming for Project PHP: Methods for developing large PHP projects (II.)





Author: Luis Argerich translator: Limodou




The object of the
"Another" class now has all the data members and methods of the parent class (something), plus its own data into


and methods.





You can use


$obj 2=new something;


$obj 2->setx (6);


$obj 2->sety (7);





PHP does not now support multiple inheritance, so you cannot derive new classes from two or more than two classes.





you can redefine a method in a derived class, and if we redefine the Getx method in the "Another" class, we can't make the


uses the Getx method of "something". If you declare a data member in a derived class that has the same name as Kippe, then when you deal with it,


it will "hide" the data members of the base class.





you can define constructors in your class. A constructor is a method that has the same name as a class name and is
when you create an object of a class

, for example:





--------------------------------------------------------------------------------


<?php





class Something {


var $x;





function Something ($y) {


$this->x= $y;


}





function SetX ($v) {


$this->x= $v;


}





function GetX () {


return $this->x;


}


}





?>--------------------------------------------------------------------------------


so you can create an object, through:





$obj =new Something (6);




The
constructor automatically assigns 6 to the data variable x. Constructors and methods are common PHP functions, so you can use the default parameters.





function Something ($x = "3", $y = "5")





Then:





$obj =new Something (); X=3 and Y=5


$obj =new Something (8); X=8 and Y=5


$obj =new Something (8,9); X=8 and Y=9





The default parameter uses C + +, so you can't ignore the value of Y, and give X a default parameter, which is assigned from left to right if


the parameters passed in are less than the required parameters, they will use the default parameters.





when an object of a derived class is created, only its constructors are invoked, and the constructor of the parent class is not invoked, if you want to call the base


class constructor, you must display the call in the constructor of the derived class. You can do this because the methods of all the parent classes in a derived class are


is available.





--------------------------------------------------------------------------------


<?php





function Another () {


$this->y=5;


$this->something ();


//Display calls the base class constructor


}





?>--------------------------------------------------------------------------------

A good mechanism for
oop is to use abstract classes. An abstract class is not instantiated and can only be supplied to a derived class as an interface. Designers usually


uses abstract classes to force programmers to derive from a base class, which ensures that the new class contains some expected functionality. There is no standard method in PHP,


but:





If you need this feature, you can define the base class and add a "die" call after its constructor so that the base

The
class is not instantiated and is now preceded by a "die" statement after each method (interface), so if a programmer does not have
in a derived class

overrides method, an error is raised. And because PHP is untyped, you may need to verify that an object is derived from your base class


class, add a method in the base class to the identity of the real class (return some identity id) and validate
when you receive an object parameter

this value. Of course, if an evil-bad programmer overrides this method in a derived class, this method will not work, but the general

The
problem is more of a lazy programmer than an evil one.





Of course, it's nice to be able to make the base class impossible for programmers to see, just print the interface to do their job.





there is no destructor in PHP.








Transferred from Phpbuilder.com