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PHP 中的条件 switch 语句

[英]Conditional switch statements in PHP

I'm quite used to vb.net's Select Case syntax which is essentially a switch statement, where you can do things like Case Is > 5 and if it matches, it will execute that case.我非常习惯 vb.net 的Select Case语法,它本质上是一个 switch 语句,您可以在其中执行Case Is > 5之类的操作,如果匹配,它将执行该 case。

How can I do what I'm going to call "conditional switch statements" since I don't know the actual name, in PHP?由于我不知道 PHP 中的实际名称,我该如何做我将称之为“条件切换语句”的事情?

Or, what's a quick way to manage this?或者,什么是管理它的快速方法?

switch($test)
{
    case < 0.1:
        // do stuff
        break;
}

That's what I've tried currently.这就是我目前尝试过的。

I think you're searching for something like this (this is not exactly what you want or at least what I understand is your need).我认为你正在寻找这样的东西(这不完全是你想要的,或者至少我理解的是你的需要)。

switch (true) finds the cases which evaluate to a truthy value, and execute the code within until the first break; switch (true)查找评估为真值的情况,并在第一次中断之前执行其中的代码; it encounters.它遇到。

<?php

switch (true) {

case ($totaltime <= 1):
echo "That was fast!";
break;

case ($totaltime <= 5):
echo "Not fast!";
break;

case ($totaltime <= 10):
echo "That's slooooow";
break;
}

?>

PHP supports switch statements . PHP 支持switch 语句 Is that what you wanted?那是你想要的吗?

I tried to add this as a comment to the answer by BoltCock, but SO is telling me that his answer is locked so I'll make this a separate (and essentially redundant) answer:我试图将其添加为 BoltCock 答案的评论,但 SO 告诉我他的答案已被锁定,因此我将其作为一个单独的(并且基本上是多余的)答案:

The "switch(true)" answer from BoltCock is much like the following example , which although logically equivalent to if + else if + else is arguably more beautiful because the conditional expressions are vertically aligned, and is standard/accepted practice in PHP. BoltCock 的“switch(true)”答案很像下面的例子,虽然逻辑上等价于 if + else if + else 可以说更漂亮,因为条件表达式是垂直对齐的,并且是 PHP 中的标准/接受的做法。

But the if + else if + else syntax is essentially universal across scripting languages and therefore immediately readable (and maintainable) by anyone, which gives it my nod as well.但是 if + else if + else 语法本质上是跨脚本语言通用的,因此任何人都可以立即阅读(和维护),这也让我点头。

You can accomplish this in PHP 8.0+ with match statements .您可以在 PHP 8.0+ 中使用match statements完成此操作。

If you have a single expression in your switch statement, it is equivalent to the following match statement.如果您的 switch 语句中只有一个表达式,则它等效于以下 match 语句。 Note that unlike switch statements, we can choose to return a variable (in this code I am storing the result in $result ).请注意,与 switch 语句不同,我们可以选择返回一个变量(在此代码中,我将结果存储在$result )。

$test = 0.05;
$result = match (true) {
    $test < 0.1 => "I'm less than 0.1",
    $test < 0.01 => "I'm less than 0.01",
    default => "default",
};

var_dump($result);

Match only allows you to have a single expression on the right-hand side (everything after => ). Match 只允许您在右侧有一个表达式( =>之后的所有内容)。 The equivalent to switch statement with multi-line cases would be to use separate functions.与多行情况下的 switch 语句等效的是使用单独的函数。

function tinyCase(){}
function veryTinyCase(){}
function defaultCase(){}

$test = 0.01;
match (true) {
    $test < 0.1 => tinyCase(),
    $test < 0.1 => veryTinyCase(),
    default => defaultCase(),
};

And for reference, if you just want to check for equality you can do:作为参考,如果您只想检查相等性,您可以执行以下操作:

$result = match ($test) { // This example shows doing something other than match(true)
    0.1 => "I'm equal to 0.1",
    0.01 => "I'm equal to 0.01",
    default => "default",
};

Match statements do have some key differences from switch statements that you need to watch out for: Match 语句确实与您需要注意的 switch 语句有一些主要区别:

  • My last example will use a strict equality check === instead of a loose one == .我的最后一个例子将使用严格的相等检查===而不是松散的==
  • If a default case is not provided, an UnhandledMatchError error is thrown when nothing matches.如果未提供默认情况,则在没有匹配项时抛出 UnhandledMatchError 错误。
  • And there is no worrying about falling through to the next case if you forget to add break .如果您忘记添加break ,也不必担心会遇到下一个案例。

Switch statement with conditions带条件的 Switch 语句

switch(true)
{
    case ($car == "Audi" || $car == "Mercedes"):
        echo "German cars are amazing";
        break;
    case ($car == "Jaguar"):
        echo "Jaguar is the best";
        break;
    default:
        echo "$car is Ok";
}

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