Explanation of the relationship between classes and constructors in php

This article introduces you to the analysis of PHP classes and constructors, including class creation, fields and methods, constructors, etc.

----Creation of a class----

php uses the keyword class to create a class and uses a pair of curly brackets

For example:

class name{
public $n="";
private $u="";
public function name() {
$n="233";
$u="23333";
}
public function rename($newn){
$this->n=$newn;//this表示这个类
}
}

No semicolon at the end. Then $n, $u are fields; name() is a constructor (construct() can also define a constructor, see below for details), which can assign values ​​to fields; rename() is a method.

----Fields and methods----

Compare

$obj=new name();
echo $obj->n;

with

$obj=new name();
echo $obj->u;

The former is executable, but the latter is not possible because private is declared before $u. This is similar to c++.

Code:

public static $nm ="2333333333333333" ;

declares a static field for the function.

The variable can be accessed directly through the class name and ::

echo name::$nm;

This is also similar to c++.

In php, you can also access static fields in the class through self::+$+Variable name. At this time, self is equivalent to $this->.

----Constructor----

In php5 and earlier versions, the constructor has the same name as the class

In php5 and later versions, the magic word construct() can define the constructor

class name{
public $n="";
private $u="";
public function construct() {
$n="233";
$u="23333";
}
public function rename($newn){
$this->n=$newn;
}
}

The constructor can have parameters

construct($name="",$sex="man",$age=0){}

When declaring the object

$obj= new name("我","man",28);

If no parameters are given at this time, the default value is the value after =.

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