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This article mainly introduces how to define classes in php, which has a certain reference value, interested friends can refer to, I hope you can learn a lot after reading this article, the following let the editor take you to understand.

In php, you can define a class by using the class keyword plus the class name, and wrap the properties and methods that define the class in the class body with curly braces "{}", and the syntax "[modifies the keyword of the class] class class name {properties and methods of the class;}".

Operating environment of this tutorial: windows7 system, PHP7.1 version, DELL G3 computer

The definition method of php class

In PHP, you can define a class using the class keyword plus the class name, and then wrap the properties and methods that define the class in the class body with curly braces {}. The syntax format of the class is as follows:

[modifier class keywords] class class name {properties and methods of the class;}

Class names are similar to variable names and function names by following the custom naming rules in PHP, which can be legal tags for any non-PHP reserved word. A legal class name begins with a letter or underscore, followed by several letters, numbers, or underscores. If the class name consists of multiple words, it is customary to capitalize the first letter of each word. In addition, the class name had better have a certain meaning, not just a few letters.

The modifier class keyword is an optional parameter that can be omitted. We usually use the following keywords to modify the class:

Abstract: an abstract class or method that, after being decorated as an abstract class, cannot be instantiated, but can be inherited. If at least one method in a class is declared abstract, the class must also be declared abstract. When inheriting an abstract class, the subclass must redefine all abstract methods in the parent class, and the access control for those methods must be the same as in the parent class.

Final: classes decorated with final cannot be inherited, and methods decorated with final cannot be redefined in subclasses.

Note: a class can contain its own constants, variables (called "member properties" or "properties" in the class), and functions (called "member methods" or "methods" in the class).

Example:

Define an empty class

Class Person {}

Define a class with member properties and operations

Class Person {member attribute. Operate as.}

Define a class that cannot be inherited, using the final keyword

Final class Person {member attribute. Operate as.}

Note: the final keyword cannot be used to modify member properties, only classes and methods (described later in the final method)

Here is a class with final

Define a class FinalClass of final that contains a public function

Final class FinalClass {public function ffun () {echo "this class is a final class";}}

Define a class ChildFinalClass and inherit the FinalClass class

Class ChildFinalClass extends FinalClass {public function fchildfun () {echo 'this class inherits the final class FinalClass';}}

In this way, the system will prompt when you execute the above command

Fatal error: Class ChildFinalClass may not inherit from final class (FinalClass)

Prove that the class defined by the final keyword cannot be inherited by a subclass

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