inheritance

The three characteristics of object-oriented: encapsulation, inheritance, and polymorphism First, let’s briefly understand the abstraction:When we defined a class earlier, we actually extracted the common attributes and behaviors of a class of things , forming a physical model (template), this method of researching problems is called abstraction 1. EncapsulationEncapsulation is to encapsulate the extracted data and the operation on the data together, the data is protected inside, and other parts of the program only have authorized operations (methods ) to operate on the data. php provides three access control modifierspublic means global, inside this class, outside the class, and subclasses can accessprotected means protected, only this class or subclasses can accessprivate means private, only accessible inside this class , there is also this way of writing var $name in PHP4, which means public attributes, and this way of writing is not recommendedExample: The code is as follows: < ?php class Person{ public $name; protected $age; private $salary; function __construct($name,$age,$salary){ $this ->name=$name; $this->age=$age; $this->salary=$salary; } public function showinfo(){ //this Indicates that all three modifiers can be used inside this class. echo $this->name.”||”.$this->age.”||”.$this->salary; } } $p1=new Person(‘Zhang San’,20,3000); //This is outside the class, so if you use the following method to access…