Usage of => and -> and :: in PHP
Recommended manual:php complete self-study manual
1. Usage of =>
Array default key in php The name is an integer, you can also define any character key name yourself (preferably with practical meaning), such as:
$css=array('style'=>'0'，‘color’=>‘green‘)； 则$css['style']=='0'，$css['color']=='green'。
2, usage of ->
-> is used to reference objects Members (properties and methods);
<?php
$arr=['a'=>123,'b'=>456];//数组初始化
echo $arr['a'];//数组引用
print_r($arr);//查看数组
class A{
public $a=123;
public $b=456;
}
$obj=new A();
echo $obj->a;//对象引用
print_r($obj);//查看对象
?>Output results:
123Array(
[a] => 123
[b] => 456)
123A Object(
[a] => 123
[b] => 456)3. Usage of ::
Double colon operator is the scope limitation operator Scope Resolution Operator You can access static, const, and overridden properties and methods in classes.
(1) Program List: Use variables to access outside the class definition
<?php
class Fruit {
const CONST_VALUE = 'Fruit Color';
}
$classname = 'Fruit';
echo $classname::CONST_VALUE; // As of PHP 5.3.0
echo Fruit::CONST_VALUE;
?>(2) Program List: Use outside the class definition::
<?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();
?>(3) Program List: Call the parent method
<?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();
?>(4) Program List: Use the scope qualifier
<?php
class Apple
{
public function showColor()
{
return $this->color;
}
}
class Banana12 {
public $color;
public function __construct()
{
$this->color = "Banana is yellow";
}
public function GetColor()
{
return Apple::showColor();
}
}
$banana = new Banana;
echo $banana->GetColor();
?>(5) Program List: Call the base class method
<?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"!
?>Related article recommendations:
1.Introduction to the meaning of the double colon::range parsing operator in php
2.The difference between the double colon range parsing operator and the arrow-> operator in php
Related video recommendations:
1.Dugu Jiujian (4)_PHP video tutorial
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