php learning php learning object-oriented courseware page 1/2

The main three characteristics of objects
Object behavior: What operations can be applied to the object, turning on the light and turning off the light are behaviors.
The shape of the object: how the object responds, color, size, appearance when those methods are applied.
Representation of objects: The representation of objects is equivalent to an ID card. It specifically distinguishes the differences between the same behaviors and states.
Object-oriented model
Object-oriented concept:
oop (object-oriented programming) can make its code more concise, easier to maintain and more reproducible
What is a class:
A class is a group of objects with the same attributes and services A collection of group objects such as people, books, ships, and cars all belong to classes. They make a unified abstract description for the objects belonging to this class. In programming languages, a class is a separate program, and it should have a class name. Includes two parts: attribute description and service.
What is an object:
An object is an entity in the system that describes objective events. It is a basic unit that constitutes the system. *Data and code are bundled in an entity*. An object consists of a set of properties and a set of behaviors that operate on this set of properties.
From an abstract point of view, an object is an abstraction of something in the problem domain or implementation domain. It reflects the information saved and the role played by the thing in the system: it is a set of properties and an encapsulation body that has the authority to operate on these properties. The objective world is composed of objects and the connections between objects.
The relationship between classes and objects:
The relationship between classes and objects is like the relationship between molds and castings. The result of the strength of the class is the object, and the abstraction of the object is the class. A class describes a group of objects with the same characteristics (attributes) and Objects with the same behavior.
Classes, attributes and methods
Class syntax format defined in PHP:
class classname [optional attribute]{
public $property [=value];... // Use public to declare a public identifier and then give it to a variable. Variables can also be used Assignment
function functionname (args){ //Member function in class method
Code}...
//Class method (member function)
}
Generate object (instantiation of class): $object name=new classname( );
Use the properties of the object
In a class, you can access a special pointer $this. When the variable is set or accessed through an operation in the class, use $this->name to reference.
The object Generate
After defining the class, use a new statement to declare it. Due to the encapsulation characteristics of object data, the object cannot be directly accessed by the main program block. The attributes and behavior functions defined in the class must be called through the object to achieve access indirectly. Control the purpose of the data in the class.
The relationship between objects and classes
The relationship between objects and classes:
Objects actually exist and occupy dynamic resources.
A class is a blueprint of an object and may occupy static resources.
Object attributes occupy dynamic resources
Class (static) attributes are actually "global variables" on the class namespace
Performance considerations:
Each object occupies separate data space
The increased calling level may consume execution time
Method Parameter form and transfer method
The parameters of the method can be basic data types, arrays and class objects.
  Basic data type: Pass by value parameter
  Array: Pass by value parameter
  Class object: Pass by reference
  Constructor
The constructor plays the role of initialization in the class
The generation method of the constructor is the same as other functions, except that its name must be __construct().
Grammar format: function __construct(parameter){
. . . . . . . .例}
Example:
Class Person {
public $ name;
public $ sex;
public $ Age; & lt; br & gt; "" ;
            $this->name=$name;                                                                                                                                                                 When the object is in scope (for example, the function in which the object is located has been called), the system automatically executes the destructor. Memory should be released in the destructor before exiting.
Destructor__destruct The destructor does not have any parameters
Example: class person{
function _ _destruct()
{ echo "bye bye!"; }
}
$a=new person();
Access type
public Public (public modifier) ​​can be accessed both inside and outside the class
private (private modifier) ​​can only be accessed inside the class
protected (protected member modifier) ​​can be accessed by subclasses but not outside the class Access the three important features of
oop
Encapsulation, inheritance, polymorphism
Encapsulation: Encapsulation is to combine the properties and behavior of an object into an independent unit.
Encapsulating a class requires two steps. The first step is to privatize a class. The second step is to use set and get to read and assign values.
The advantage is that it hides the implementation details of the class and can easily add logic control and restrictions. Unreasonable operations on attributes can be easily modified to enhance the maintainability of the code.
__get and __set
Generally speaking, it is more realistic to make the class private.
Two predefined functions are used to obtain and apply values.
__get The value obtained is usually the value of the domain
__set The value set is usually the value of the domain
__call When a method that does not exist in an object is called, an error will occur. The call() method is used to handle this situation.

Current page 1/2 12Next page

The above introduces the php learning php learning object-oriented courseware page 1/2, including the content of php learning. I hope it will be helpful to friends who are interested in PHP tutorials.