Switch 语句返回错误结果

问题描述

晕！我不确定我的 switch 语句哪里出错了！这是我希望我的代码执行的操作:

Halo! I am not sure where I am going wrong in my switch statement! Here's what I want my code to do:

如果三个变量都为空，那么我不希望任何事情发生.但是，如果没有，那么我想看看哪些是空的，哪些不是，并根据它们的状态执行不同的任务.

If all three variables are empty, then I want nothing to happen. However, if not, then I want to see which ones are empty and which ones are not and perform different tasks based on their state.

如果它们不为空，那么我想在变量之前添加一个字符串.如果它们是空的，那么我想添加一个字符串，说明..PLEASE PROVIDE INFORMATION".

If they're not empty then I want to add a string before the variable. If they're empty, then I want to add a string stating "..PLEASE PROVIDE INFORMATION".

使用当前的硬编码变量，它应该返回:

With the current hard coded variables, it should return:

Airline Name: United
Flight Number: 262
Departure Airport: PLEASE PROVIDE DEPARTURE AIRPORT

但它返回:

Airline Name: PLEASE PROVIDE AIRLINE NAME
Flight Number: PLEASE PROVIDE FLIGHT NUMBER
Departure Airport: PLEASE PROVIDE DEPARTURE AIRPORT

代码:

$airline_name = "United";
$flight_number = 262;
$departure_airport = "";

function airport($one, $two, $three) {

if ($one =="" && $two =="" && $three =="") {
} else {
    switch(true) {
        case !empty($one):
        $one = "Airline Name: $one<br>";
        case empty($one):
        $one = "Airline Name: PLEASE PROVIDE AIRLINE NAME<br>";
        case !empty($two):
        $two = "Flight Number: $two<br>";
        case empty($two):
        $two = "Flight Number: PLEASE PROVIDE FLIGHT NUMBER<br>";
        case !empty($three):
        $three = "Departure Airport: $three<br>";
        case empty($three):
        $three = "Departure Airport: PLEASE PROVIDE DEPARTURE AIRPORT<br>";
    }

    }
echo $one, $two, $three;
}

airport($airline_name,$flight_number,$departure_airport);

?>

推荐答案

您想要的行为可以通过 if else 或三元运算符来实现(这几乎只是一种快捷方式编写if/else).这是一个未经测试的粗略示例.

The behavior you want would be achieved with an if else, or the ternary operator (which is pretty much just a short hand way of writing an if/else). Here's a rough untested example.

function airport($one, $two, $three) {
   if ( !empty($one) || !empty($two) || !empty($three) ) {
         $one = !empty($one) ? "Airline Name: $one<br>" :"Airline Name: PLEASE PROVIDE AIRLINE NAME<br>";
         $two = !empty($two) ? "Flight Number: $two<br>" : "Flight Number: PLEASE PROVIDE FLIGHT NUMBER<br>";
         $three = !empty($three) ? "Departure Airport: $three<br>" : "Departure Airport: PLEASE PROVIDE DEPARTURE AIRPORT<br>";
   }
   echo $one, $two, $three;
}
airport($airline_name,$flight_number,$departure_airport);

至于为什么您的 switch 没有按照您的预期执行，根据手册:

As to why your switch doesn't perform as you expect, per the manual:

只有当 case 语句的值与 switch 表达式的值匹配时，PHP 才会开始执行这些语句.PHP 会继续执行语句，直到 switch 块结束，或者第一次看到 break 语句. 如果没有在 case 语句列表的末尾编写 break 语句，PHP将继续执行以下案例的语句.

-http://php.net/manual/en/control-structures.switch.php

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