final static $this keyword study notes in php_PHP tutorial-PHP Tutorial-php.cn

final static $this keyword study notes in php_PHP tutorial

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Release： 2016-07-13 17:15:40

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In php, the final static $this keyword is mainly used in classes or objects. Now I will record my notes on learning final static $this. Friends who need to know more can refer to it.

final keyword

php final keyword is used in front of a function or class name to indicate that the function cannot be overridden or the class cannot be inherited.

1. The final method cannot be overridden.

If you do not want a method in the class to be overridden by subclasses, you only need to add the keyword final before the method, that is, set the final method.

Example:

The code is as follows

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代码如下	复制代码
class ex1{ final function fn1(){ return "php"; } } class ex2 extends ex1{ function fn1(){ return "html"; } } $p= new ex2(); echo $p->fn1(); ?>

class ex1{
final function fn1(){
Return "php";
}
}
class ex2 extends ex1{
function fn1(){
Return "html";
}
}
$p= new ex2();
echo $p->fn1();
?>

Methods with the final keyword cannot be overridden and an error occurs.

2. Final classes cannot be inherited.

A class declared final cannot be inherited, otherwise an error will occur.

Example:

代码如下	复制代码
final class ex1{ private $name; } class ex2 extends ex1{ private $age; } ?>

The code is as follows	Copy code
final class ex1{ private $name; } class ex2 extends ex1{ private $age; } ?>

static keyword

The php static keyword can not only be used to declare a static variable, but can also declare static attributes or methods in a class, becoming "class attributes" or "class methods".

1. After declaring static attributes and methods, you cannot use the $this keyword to reference them in the class. You can use the following two methods to reference them:

In class: self::static member name

Outside the class: class name::static member name

2. When accessing this class, you do not need to instantiate it. You can directly use the format of class name::static member name.

代码如下	复制代码
class user{ private static $count = 10; private static $sum=1; public function __construct(){ for($i=1;$i<11;$i++){ self::$sum = self::$sum * self::$count; /* 调用静态变量 */ self::$count--; } } public function getCount(){ return self::$sum; } } $user1 = new user(); echo $user1->getCount(); ?>

Static property instance:

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private static $count = 10; private static $sum=1; public function __construct(){ for($i=1;$i<11;$i++){ self::$sum = self::$sum * self::$count; /* Call static variables */ self::$count--; } } public function getCount(){ return self::$sum; } } $user1 = new user(); echo $user1->getCount(); ?>

Static method instance:

$this keyword

The code is as follows

代码如下

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class Math{
public static function sum($num1,$num2){
return $num1 + $num2;
}
public static function product($num1,$num2){
return $num1 * $num2;
}
}
$a = 88;
$b = 100;
echo "两数之和为： ";
echo "
";
echo Math::sum($a,$b);
echo "

";
$a = 66;
$b = 88;
echo "两数之积为： ";
echo "
";
echo Math::product($a,$b);
?>

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return $num1 + $num2;

}

public static function product($num1,$num2){
return $num1 * $num2;
}
}

$a = 88; $b = 100;

echo "The sum of the two numbers is: ";

echo "
";

echo Math::sum($a,$b);

echo "

"; $a = 66; $b = 88; echo "The product of two numbers is: "; "

代码如下	复制代码
class user{ private $n; function __construct(){ $name="Mike"; echo $this->n=$name; } } $p=new user(); ?>

echo "
";

echo Math::product($a,$b);
?>

代码如下	复制代码
class cal{ public function sum($a,$b){ return $a+$b; } public function prt($a,$c){ return $a$c; } public function result($a,$b,$c){ $a=$this->sum($a,$b); return $this->prt($a,$c); } } $c=new cal(); echo "(2+3)10= " .$c->result('2','3','10'); ?>

In order to solve the naming conflict and uncertainty problem of variables and attributes in PHP classes and objects, the "$this" keyword is introduced to call the current object. When calling the properties and methods of the current object in a class, you must use the "$this->" keyword; $this in the constructor refers to the new object created by the constructor; The local variables within the method do not belong to the object, and the $this keyword is not used to obtain the value. Using the $this keyword, we can call object properties or methods in the class. 1. Call variables Example:

The code is as follows

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class user{<🎜> private $n;<🎜> function __construct(){<🎜> $name="Mike";<🎜> echo $this->n=$name; } } $p=new user(); ?> 2. Call method Example:

The code is as follows

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class cal{<🎜> public function sum($a,$b){<🎜> Return $a+$b;<🎜> }<🎜> public function prt($a,$c){<🎜> Return $a*$c;<🎜> }<🎜> public function result($a,$b,$c){<🎜> $a=$this->sum($a,$b); Return $this->prt($a,$c); } } $c=new cal(); echo "(2+3)*10= " .$c->result('2','3','10'); ?>