In-depth understanding of PHP class and constructor analysis

Everyone has a certain understanding of classes. Here we only introduce the noteworthy aspects of classes in php

----Creation of classes----

php Use the keyword class to create a class, and use a pair of braces
such as:

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
  }
}

without a semicolon at the end. Then $n,$u is a field; name() is a constructor (construct() can also define a constructor, see below for details), which can assign values ​​to fields; rename() is a method.

----Field----

Comparison
$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++.

You can also access static fields in the class through self::+$+variable name . At this time, self is equivalent to $this-> ;.

The use of methods is similar to fields

##----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

The magic word construct() can define a 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 an object

$obj= new name("我","man",28);

If no parameters are given, the value after = will be defaulted.

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