Double colon::Usage in PHP, colon php usage_PHP tutorial-PHP Tutorial-php.cn

Double colon::Usage in PHP, colon php usage_PHP tutorial

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Release： 2016-07-12 09:05:24

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Usage of double colon:: in PHP, usage of colon php

A few days ago on Baidu I saw someone asking about the usage of double colon:: in PHP. The answer I gave him at that time was relatively concise because typing on a mobile phone was not very convenient! It suddenly occurred to me today, so here is a summary of the situations I encountered using double colon:: in PHP!

The double-colon operator, the Scope Resolution Operator, can access static, const, and overridden properties and methods in classes.
If used outside a class definition, call it using the class name. In PHP 5.3.0, you can use variables instead of class names.

Program List: Use variables to access outside the class definition

<&#63;php
class Fruit {
 const CONST_VALUE = 'Fruit Color';
}
$classname = 'Fruit';
echo $classname::CONST_VALUE; // As of PHP ..
echo Fruit::CONST_VALUE;
&#63;>
Program List：在类定义外部使用::
<&#63;php
class Fruit {
 const CONST_VALUE = 'Fruit Color';
}
class Apple extends Fruit
{
 public static $color = 'Red';
 public static function doubleColon() {
  echo parent::CONST_VALUE . "\n";
  echo self::$color . "\n";
 }
}
Apple::doubleColon();
&#63;>

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Program execution result:

Fruit Color Red

Program List: Call parent method

<&#63;php
class Fruit
{
 protected function showColor() {
  echo "Fruit::showColor()\n";
 }
}
class Apple extends Fruit
{
 // Override parent's definition
 public function showColor()
 {
  // But still call the parent function
  parent::showColor();
  echo "Apple::showColor()\n";
 }
}
$apple = new Apple();
$apple->showColor();
&#63;>

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Program execution result:

Fruit::showColor()
Apple::showColor()

Program List: Use scope qualifier

<&#63;php
 class Apple
 {
  public function showColor()
  {
   return $this->color;
  }
 }
 class Banana
 {
  public $color;
  public function __construct()
  {
   $this->color = "Banana is yellow";
  }
  public function GetColor()
  {
   return Apple::showColor();
  }
 }
 $banana = new Banana;
 echo $banana->GetColor();
&#63;>

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Program execution result:

Banana is yellow

Program List: Method of calling base class

<&#63;php
class Fruit
{
 static function color()
 {
  return "color";
 }
 static function showColor()
 {
  echo "show " . self::color();
 }
}
class Apple extends Fruit
{
 static function color()
 {
  return "red";
 }
}
Apple::showColor();
// output is "show color"!
&#63;>

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Program execution result:

show color

The above content has been explained in detail to you:: its usage in PHP. I hope you like it.