php - 如何在 PHP 中使用带有整数 0 的开关？

Question

将整数 0 作为开关参数将采用第一个结果“foo”:

$data=0; // $data is usually coming from somewhere else, set to 0 here to show the problem
switch ($data) :
    case "anything":
        echo "foo";
        break;
    case 0:
        echo "zero";
        break;
    default: 
        echo "bar";
endswitch;

如何更改此设置，以便开关按预期写入“零”？

Answer 1

switch/case 语句使用松散比较，不管喜欢与否，0 == "anything"是 true :

Comparison Operators

[...] If you compare a number with a string or the comparison involves numerical strings, then each string is converted to a number and the comparison performed numerically. These rules also apply to the switch statement. [...]

var_dump(0 == "a"); // 0 == 0 -> true

一种解决方案是将所有 case 语句更改为字符串，并进行字符串比较:

$data = 0;
switch ((string) $data): ## <- changed this
    case "anything":
        echo "foo";
        break;
    case "0":            ## <- and this
        echo "zero";
        break;
    default: 
        echo "bar";
endswitch;