Question

我使用下面的示例代码：

<?php
$id = "a";
echo $id == "a" ? "Apple" : $id == "b" ? "Bat" : $id == "c" ? "Cat" : $id == "d" ? "Dog" : "Others";

我希望输出 Apple 。但我得到了狗。任何人都可以帮助我。

Answer 1

关于三元运算符的注释：http://www.php.net/manual/en/language.operators.comparison.php

<?php
// on first glance, the following appears to output 'true'
echo (true?'true':false?'t':'f');

// however, the actual output of the above is 't'
// this is because ternary expressions are evaluated from left to right

// the following is a more obvious version of the same code as above
echo ((true ? 'true' : false) ? 't' : 'f');

// here, you can see that the first expression is evaluated to 'true', which
// in turn evaluates to (bool)true, thus returning the true branch of the
// second ternary expression.
?>

Answer 2

<方式＃1

使用switch代替它也可以帮助您的代码更具可读性。

switch($id)
{
    case "a":
        echo "Apple";
        break;

    case "b":
        echo "Bat";
        break;

    //Your code...

    //More code..
}

<方式＃2

您还可以使用array_key_exists()

$id = "a";
$arr = ["a"=>"Apple","b"=>"Bat"];
if(array_key_exists($id,$arr))
{
    echo $arr[$id]; //"prints" Apple
}

Answer 3

尝试

echo $id == "a" ? "Apple" : ($id == "b" ? "Bat" : $id == "c" ? "Cat" : $id == "d" ? "Dog" : "Others");

如果条件为false，那么只有我在()中放置的剩余块才会执行。

Answer 4

<?php

$id = "a";

echo $id == "a" ? "Apple" : ($id == "b" ? "Bat" : ($id == "c" ? "Cat" : ($id == "d" ? "Dog" : "Others")));

Answer 5

尝试将您的条件分开

echo ($id == "a" ? "Apple" : ($id == "b" ? "Bat" : $id == "c" ? "Cat" : $id == "d" ? "Dog" : "Others"));

否则使用switch()会更好

Answer 6

这是：

<?php
$id = "a";
echo $id == "a" ? "Apple" : ($id == "b" ? "Bat" : $id == "c" ? "Cat" : $id == "d" ? "Dog" : "Others");
?>

Answer 7

将else条件部分放在括号中：

echo $id == "a" ? "Apple" : ($id == "b" ? "Bat" : $id == "c" ? "Cat" : $id == "d" ? "Dog" : "Others");

参考operator precedence

PHP短代码条件不起作用

7 个答案: