PHP8两个令人激动的特性:JIT和match表达式

2020-07-1709:00:39后端程序开发Comments2,145 views字数 2655阅读模式

PHP8带来两个最令人激动的特性:JIT和match表达式。关于PHP8 JIT有很多材料已经予以论述,我们不再赘述,参考鸟哥的blog(风雪之隅)文章可以学习。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

PHP8两个令人激动的特性:JIT和match表达式

本文我们要说另一个新引入的语法match表达式语法,可以说是PHP 8引入的最好的功能之一,它使用类似switch的语法。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

基本功能文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

$status = match($request_method) {文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

'post' => $this->handlePost(),文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

'get', 'head' => $this->handleGet(),文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

default => throw new \Exception('Unsupported'),文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

};文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

用switch...case做对比,要实现上面的功能,代码要略繁琐一点:文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

switch ($request_method) {文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

case 'post':文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

$status = $this->handlePost();文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

break;文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

case 'get':文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

case 'head':文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

$status = $this->handleGet();文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

break;文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

default:文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

throw new \Exception('Unsupported');文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

};文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

相比switch, match会直接返回值,无需中间变量(比如上例中的$status)。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

表达式可以返回一个值文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

在每个分支可以被分配给一个变量。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

$name = match(2) {文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

1 => 'One',文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

2 => 'Two',文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

};文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

echo $name; // "Two"文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

不必再将返回值分配给其他中变量,匹配的语句返回值可直接从match表达式中返回。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

可匹配多个条件文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

match表达式可能包含一个或多个匹配条件,它们的行为类似于块中的多个级联case键switch。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

match($request_method) {文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

'post' => $this->handlePost(),文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

'get', 'head' => $this->handleGet(),文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

};文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

满足$request_method === 'get'和$request_method === 'head'两个条件都会执行$this->handleGet()。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

每个分支只能包含一个表达式文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

与switch可以包含任意数量的表达式的块不同,一条match语句只能包含一个表达式。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

match($name) {文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

'XXX' =>文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

init();文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

doth();文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

};文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

上面的语法错误的。=>只能有一个表达式。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

隐含的break文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

match表达式的每个匹配分支仅允许一个表达式,并且无需switch块一样的break。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

switch ('test') {文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

case 'test':文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

$this->doTest ();文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

case 'send':文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

$this->sendmsg ();文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

}文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

在switch...caser容易犯的错误是忘记了break语句,这会使流程直接进入下一分支。在上面的switch块中,缺少break;语句会使代码$this->doTest()无法正常执行执行。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

match ('test') {文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

'test' => $this->doTest (),文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

'send' => $this->sendmsg (),文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

};文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

match表达式无需显式break语句即可工作。它只执行一个match分支,并立即返回该值。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

default分支文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

match语句支持一个default分支,该分支工作原理与switch...case块中的default情况类似。如果没有其他条件相匹配,将执行default match分支。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

match ('DEF') {文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

'aaa' => ...,文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

'bbb' => ...,文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

default => echo 'NO matching: ' . $name,文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

};文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

// "NO matchin: DEFF"文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

match表达式必须符合条件文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

switch如果没有匹配case键,则block静默进行代码流。match表达式没有。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

在match表达式中,必须存在与表达式匹配的条件或default要处理的条件。如果没有匹配项,而且为设置default分支,match表达式将会引发\UnhandledMatchError异常。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

$value = 3;文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

match($value) {文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

1 => 'One',文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

2 => 'Two',文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

};文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

上面的代码执行时候会抛出错误:文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

Fatal error: Uncaught UnhandledMatchError in ...文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

match\UnhandledMatchError如果表达式中没有匹配项,则表达式将引发异常。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

\UnhandledMatchError是PHP 8中的新异常类,它扩展了\Error。有关所有PHP核心异常类的完整层次结构。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

该类可以很容易地扩展:文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

class UnhandledMatchError extends \Error {}文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

对非强制类型的严格匹配文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

match表达式中最重要的设计选择之一是它对非强制类型的匹配。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

function read(mixed $key): string {文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

return match ($key) {文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

1 => 'Integer 1',文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

'1' => 'String 1',文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

true => 'Bool true',文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

[] => 'Empty array',文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

[1] => 'Array [1]',文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

};文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

}文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

read(1); // "Integer 1"文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

read('1'); // "String 1"文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

在典型的switch块中,其大小写是松散匹配的,即与==。在match表达式中,所有匹配的分支都经过严格的比较(===)匹配。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

在上面的代码段中,每个单独的分支都将匹配其值和类型。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

匹配任意表达式文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

match 表达式允许给定值与表达式匹配。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

match($httpst){文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

404 => 'Page not found',文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

Response::REDIRECT => 'Redirect',文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

$client->getCode() => 'Client Error',文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

$response->getCode() => 'Response Error',文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

default => 'Unknown error'文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

};文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

表达式将按照其排列顺序进行求值。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

match表达式将尝试$httpst按以下顺序进行匹配:文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

1. $httpst === 404文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

2. $httpst === Response::REDIRECT文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

3. $httpst === $client->getCode()文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

4. $httpst === $response->getCode()文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

5. default文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

如果找到正匹配,则将不会对其他分支进行尝试,直接返回。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

match VS switch文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

PHP8两个令人激动的特性:JIT和match表达式

向后兼容性影响文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

match表达式是PHP 8中的新语法。使用match表达式的代码在较旧的PHP版本中将不起作用。文章源自菜鸟学院-https://www.cainiaoxueyuan.com/bc/19746.html

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