[PHP知识库]php基础练习

match表达式

<?php
//1
// $request_method = "post";
// $status = match($request_method) { 
// 	'post' => "post", 
// 	'get', 'head' => "get_head", 
// 	default => throw new \Exception('Unsupported'), 
// };
// var_dump($status);

//2
// class test1{
// 	public function beepa(): string{
// 		return "beepa";
// 	}
// 	public function beepb(): string{
// 		return "beepb";
// 	}
// 	public function beepc(): string{
// 		return "beepc";
// 	}
// 	public function match_test(): void{
// 		$a = 'a';
// 		$b = 'b';
// 		$c = 'c';
// 		$result = match($b){
// 		    'a' => $this->beepa(),
// 		    'b' => $this->beepb(),
// 		    'c' => $this->beepc(),
// 		};
// 		var_dump($result);
// 	}
// }
// $test1 = new test1();
// $test1->match_test();

//3
//表达式
// $age = 23;
// $result = match (true) {
//     $age >= 65 => 'senior',
//     $age >= 25 => 'adult',
//     $age >= 18 => 'young adult',
//     default => 'kid',
// };
// var_dump($result);
// $text = 'Bienvenue chez nous';
// $result = match (true) {
//     str_contains($text, 'Welcome') || str_contains($text, 'Hello') => 'en',
//     str_contains($text, 'Bienvenue') || str_contains($text, 'Bonjour') => 'fr',
// };
// var_dump($result);

//4
// function fizzbuzz($num) {
//     print match (0) {
//         $num % 15 => "FizzBuzz" . PHP_EOL,
//         $num % 3  => "Fizz" . PHP_EOL,
//         $num % 5  => "Buzz" . PHP_EOL,
//         default   => $num . PHP_EOL,
//     };
// }
// for ($i = 0; $i <=100; $i++){
//     fizzbuzz($i);
// }

//5
// $error_code = (int) 400;
// $message = (string) match($error_code){
// 	200=>"OK",
//     400=>"Bad Request",
//     401=>"Unauthorized",
//     403=>"Forbidden",
//     404=>"Not Found",
//     default=>"Unknown Error"
// };
// var_dump($message);

trait

<?php
//trait 更多用多于继承 无法实例化，而是使用 use
trait Dog{
    public $name = "dog";
    public static $static = 'foo';
    public function drive(){
        echo "This is dog drive";
    }
    public function eat(){
        echo "This is dog eat";
    }
    public static function body() :void {
        echo "This is dog body";
    }

    abstract public function getName(); //抽象方法
}
class Cat{
    use Dog;
    public function drive(){
        echo "This is cat drive";
    }
    public function getName(){
        echo "This is Cat name";
    }
}


$cat = new Cat();
//$cat->drive();    //访问方法    This is cat drive
//$cat->eat();    //访问方法    This is dog eat
//echo $cat->name;     //访问属性    dog
//echo $cat::$static;  //访问静态变量    foo
//$cat::body();    //访问静态方法 This is dog body
//$cat->getName();    //抽象方法 This is Cat name

预定义接口之 ArrayAccess

<?php
class Obj implements ArrayAccess {
    private $container = array();

    public function __construct() {
        $this->container = array(
            "one"   => 1,
            "two"   => 2,
            "three" => 3,
        );
    }

    public function offsetSet($offset, $value): void {
        if (is_null($offset)) {
            $this->container[] = $value;
        } else {
            $this->container[$offset] = $value;
        }
    }

    public function offsetExists($offset): bool {
        return isset($this->container[$offset]);
    }

    public function offsetUnset($offset): void {
        unset($this->container[$offset]);
    }

    //mixed 多种不同类型
    public function offsetGet($offset): mixed {
        return isset($this->container[$offset]) ? $this->container[$offset] : null;
    }
}

$obj = new Obj;

//var_dump($obj["two"]);  //offsetGet
//unset($obj["two"]);    //offsetUnset
//var_dump(isset($obj["two"])); //offsetExists
//$obj["two"] = "A value";    //offsetSet
//var_dump($obj["two"]);
//$obj[] = 'Append 1';
//$obj[] = 'Append 2';
//$obj[] = 'Append 3';
//print_r($obj);

//魔术方法
class Obj2{
    public $data;
    public function __construct() {
        $this->data = array(
            "one"   => 1,
            "two"   => 2,
            "three" => 3,
        );
    }
    /**
     * 以对象的方式访问数组中的数据
     *
     * @param $key
     * @return mixed
     */
    public function __get($key): mixed
    {
        return $this->data[$key];
    }
    /**
     * 以对象方式添加一个数组元素
     *
     * @param $key
     * @param $val
     */
    public function __set($key, $val): void
    {
        $this->data[$key] = $val;
    }

    /**
     * 以对象方式判断数组元素是否设置
     *
     * @param $key
     * @return bool
     */
    public function __isset($key): bool
    {
        return isset($this->data[$key]);
    }

    /**
     * 以对象方式删除一个数组元素
     *
     * @param $key
     */
    public function __unset($key): void
    {
        unset($this->data[$key]);
    }
}
$obj2 = new Obj2;
$obj2->one = "A value";    //__set
//var_dump($obj2->one);  //__get
//unset($obj["one"]);    //__unset
//var_dump(isset($obj["two"])); //__isset
//__set
$obj2->Append1 = 'Append 1';
$obj2->Append2 = 'Append 2';
$obj2->Append3 = 'Append 3';
print_r($obj2);

枚举

Enum 定义

<?php

//Enum 定义 枚举可以定义零个或多个case，且没有最大数量限制
enum Suit{
	case Hearts;
	case Diamonds;
    case Clubs;
    case Spades;
}

/**
//枚举的形参传入
function pick_a_card(Suit $suit) {
	var_dump($suit);
}
$val = Suit::Diamonds;
pick_a_card($val);
pick_a_card(Suit::Clubs);
pick_a_card('Spades');	//err
*/

/**
//每个case是该名称对象的单例
$a = Suit::Spades;
$b = Suit::Spades;
var_dump($a === $b); // true
//instanceof（1）判断一个对象是否是某个类的实例，（2）判断一个对象是否实现了某个接口。
var_dump($a instanceof Suit);  // true
*/

//所有的 case 有个只读的属性 name。 它大小写敏感，是 case 自身的名称。
print Suit::Spades->name;
print Suit::Diamonds->name;

回退（Backed）枚举

<?php
//BackedEnum  回退（Backed）枚举 

//注意枚举定义中的类型声明。它表示所有枚举值都是给定类型的。仅 int 和 String 被允许作为枚举值。
enum Suit: string
{
    case Hearts = 'H';
    case Diamonds = 'D';
    case Clubs = 'C';
    case Spades = 'S';
}
/**
//所有的 case 有个只读的属性 value。 它是定义时指定的值。
print Suit::Spades->value;
print Suit::Diamonds->value;
*/

/***
//只读性,不可修改
$suit = Suit::Clubs;
$ref = &$suit->value;	// Error: Cannot acquire reference to property Suit::$value
*/

/**
$suit =  Suit::from('X');  // || Suit::from('H'); Suit::Hearts
// 无效数据抛出 ValueError："X" is not a valid scalar value for enum "Suit"
print $suit->value;

$suit = Suit::tryFrom('A') ?? Suit::Spades;
// 无效数据返回 null，因此会用 Suit::Spades 代替。
print $suit->value;
*/
?>

枚举方法

<?php

interface Colorful{
	public function color(): string;
}
//trait
trait Rectangle
{
    public function shape(): string {
        return "trait Rectangle";
    }
}

enum Suit implements Colorful{
    use Rectangle;
	case Hearts;
    case Diamonds;
    case Clubs;
    case Spades;
    // 满足 interface 契约。
    public function color(): string{
    	return match($this){
    		Suit::Hearts, Suit::Diamonds => 'Red',
    		Suit::Clubs, Suit::Spades => 'Black',
    	};
    }
    // 不是 interface 的一部分；也没问题
    public function SuitShape(): string{
    	return "SuitShape";
    }
}
function paint(Colorful $c) {
    echo $c->name;
}
function paint_color(Colorful $c) {
    echo $c->color();
}
// paint_color(Suit::Clubs);
// paint(Suit::Clubs);  // 正常
// print (Suit::Diamonds->color());  //Black
// print(Suit::Diamonds->SuitShape()); // 输出 "SuitShape"
// print(Suit::Diamonds->shape()); // 输出 "trait Rectangle"

// var_dump(Suit::cases());    //返回全部条目 [Suit::Hearts, Suit::Diamonds, Suit::Clubs, Suit:Spades]


// Suit::Hearts === unserialize(serialize(Suit::Hearts));
// Suit::Hearts === "1";
print serialize(Suit::Hearts);  // E:11:"Suit:Hearts";

enum Foo {
    case Bar;
}

enum Baz: int {
    case Beep = 5;
}

// print_r(Foo::Bar);
// print_r(Baz::Beep);
/* 
Foo Enum (
    [name] => Bar
)
Baz Enum:int {
    [name] => Beep
    [value] => 5
}
*/

枚举静态方法

<?php
//枚举静态方法
enum Size{
	case Small;
	case Medium;
	case Large;

	public const Huge = self::Large;	//枚举静态变量

	public static function fromLength(int $cm): static{
		return match(true){
			$cm < 50 => static::Small,
            $cm < 100 => static::Medium,
            default => static::Large,
		};
	}
}
// var_dump(Size::fromLength(1));
var_dump(Size::Huge);

范例用法

<?php
enum UserStatus: string {
    case Pending = 'P';
    case Active = 'A';
    case Suspended = 'S';
    case CanceledByUser = 'C';

    public function label(): string
    {
        return match($this) {
            static::Pending => 'Pending',
            static::Active => 'Active',
            static::Suspended => 'Suspended',
            static::CanceledByUser => 'Canceled by user',
        };
    }
}

foreach (UserStatus::cases() as $case) {
    printf('<option value="%s">%s</option>\n', $case->value, $case->label());
}