What are the methods or attributes of the php object?

In PHP objects, methods refer to functions created in the class structure, which implement a behavior in the class and are part of the class; while attributes refer to variables directly declared in the class structure, in the object There can be multiple attributes, and each variable stores different attribute information of the object.

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

First of all, let’s briefly understand the related concepts:

• Class: class is the outermost structure that defines the object-oriented subject. It is also used to wrap the subject data and functions (functions). A class is a type of common affairs. Representative represents the commonality of affairs.

• Object: Object is a specific representative of a certain type of transaction and a specific unit of actual data and functional operations. It is also called an instance.

• Instantiation: new, the process of obtaining a specific instance that conforms to the abstract concept from an abstract concept.

• ##Class members: member refers to all the contents in the class structure. There are three types of class members;

• Method: Method is essentially a function created in the class structure, also called a member method, or member function.

• Property: Property is essentially a variable created in the class structure, also called a member variable.

Let’s focus on properties and methods.

Member attributes

Variables declared directly in a class are called member attributes (can also be called member variables). Multiple variables can be declared in a class, that is There can be multiple member attributes in an object, and each variable stores different attribute information of the object. The syntax format is as follows:

访问权限修饰符 属性名称 = 属性值;

The type of member attributes can be scalar types and composite types in PHP, so it can also be objects instantiated by other classes, but it is meaningless to use resources and empty types in classes .

As we mentioned before, no keyword modification is required when declaring a variable. However, when declaring member properties in a class, a keyword must be used in front of the variable to modify it, such as public, private, static, etc., but The variables modified by these keywords have certain meanings. If you do not need any modification with specific meaning, you can use the "var" keyword. Once the member attributes are modified with other keywords, you need to remove "var".

Commonly used access permission modifiers and their meanings are as follows:

• public: public, can be used inside the class, in subclasses, or outside the class , unrestricted;

• protected: protected, can be used inside the class and subclasses, but cannot be used outside the class;

• private: Private, can only be used inside the class, and cannot be used outside the class or in subclasses.

Note: A class, that is, all the content between a pair of curly brackets must be in a piece of code, that is, between a Cannot be divided into multiple pieces.

[Example] Create a Students class and declare some member attributes in the class. The code is as follows:

<?php
    class Students{
        var $name;
        public $age;
        private $sex;
        public static $school;
    }
?>

Tip: Permission modifiers can be mixed with the keyword static that defines static variables. used together as shown in the code above.

Member methods

Functions defined in a class are called member methods. The only difference between functions and member methods is that functions implement an independent function, while member methods implement a behavior in the class and are part of the class.

You can declare multiple member methods in a class. The declaration of member methods is exactly the same as the declaration of functions. However, when declaring member methods, you can add some access modifiers in front of the function keyword to control access. Permissions, such as public, private, protected, etc.

Another thing to note is that the declared member methods must be related to the class and cannot be some meaningless operations. For example, when declaring the student class, if you declare the "flying" member method, every student instantiated can fly. This is a design error.

[Example] Create some member methods in the Students class created in the above example.

<?php
    class Students{
        var $name;
        public $age;
        private $sex;
        public static $school;
        public function Write(){
           
        }
        protected static function Read(){
        }
        function Listen(){
           
        }
    }
?>

The permission modifier in front of the member method can be omitted. If omitted, the default permission is public. The declaration of member attributes and member methods in a class is optional and can exist at the same time or separately, depending on the actual situation.

In PHP7, type declarations are introduced. We can declare types for the formal parameters and return values ​​of member methods. The format is as follows:

[权限修饰符] function 方法名 (类型 参数1, 类型 参数2, ..., 类型 参数n) : 返回值类型 {
    ... ...
}

The parameter types supported in PHP7 include integers. type, float, string and Boolean types. The sample code is as follows:

<?php
    class Students{
        var $name;
        public $age;
        private $sex;
        public static $school;
        public function Write(string $a, int $b):bool{
           
        }
        protected static function Read(string $str):int{
        }
        function Listen(int $num):bool{
        }
    }
?>

Instantiate the object and access the members in the object

The object contains member properties and member methods, access the members in the object Members are similar to accessing elements in an array. Members in an object can only be accessed through a reference to the object. But a special operator -> must be used to complete the access to the members of the object. The syntax format for accessing the members of the object is as follows:

变量名 = new 类名(参数);   //实例化一个类
变量名 -> 成员属性 = 值;   //为成员属性赋值
变量名 -> 成员属性;           //直接获取成员属性的值
变量名 -> 成员方法();        //访问对象中的成员方法

下面通过一个示例来演示一下：

<?php
header("Content-type:text/html;charset=utf-8");
class Website{
    public $name, $url, $title;
    public function demo(){
        echo &#39;成员方法 demo()&#39;;
    }
}
$student = new Website();
$student -> name = &#39;php中文网&#39;;
$student -> url = &#39;https://www.php.cn/&#39;;
$student -> title = &#39;实例化对象&#39;;
echo $student -> name.&#39;<br>&#39;;
echo $student -> url.&#39;<br>&#39;;
echo $student -> title.&#39;<br>&#39;;
$student -> demo();
?>

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