PHP- 带条件开关的 Switch case 语句

Question

我可以将条件语句放在 switch 语句中吗？ ex - switch ($totaltime<=13) 除了php，其他语言的兼容性如何？

$totaltime=15;

switch ($totaltime<=13) {

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

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

case ($totaltime >= 10 && $totaltime<=15):
echo "That's slooooow";
break;
}

编辑

$totaltime=12; 
switch (false) { 
case ($totaltime <= 1): 
echo "That was fast!"; 
break; 
case ($totaltime <= 5): 
echo "Not fast!";
break;
case ($totaltime >= 10 && $totaltime<=13): 
echo "That's slooooow"; 
break; 
default: // do nothing break; 
} 

绅士在这种情况下为什么总是将输出显示为“太快了！”？

Answer 1

Switch 只检查第一个条件是否等于第二个条件，这样：

switch (CONDITION) {
    case CONDITION2:
        echo "CONDITION is equal to CONDITION2";
    break;
}

所以你必须这样做：

switch (true) {
    case $totaltime <= 1: #This checks if true (first condition) is equal to $totaltime <= 1 (second condition), so if $totaltime is <= 1 (true), is the same as checking true == true.
        echo "That was fast!";
    break;

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

    case $totaltime >= 10 && $totaltime<=13:
        echo "That's slooooow";
    break;
}

相反，我将使用if-elseif语句。 乍一看更容易理解：

if ($totaltime <= 1) {
    echo "That was fast!";
} elseif($totaltime <= 5) {
    echo "Not fast!";
} elseif($totaltime >= 10 && $totaltime<=13) {
    echo "That's slooooow";
}

Answer 2

是的，你可以（除了开关内的比较）

$totaltime=12;

switch (true) {

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

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

case ($totaltime >= 10 && $totaltime<=13):
echo "That's slooooow";
break;

default:
// do nothing
break;
}

Answer 3

是的，你可以，从 PHP 的 switch 文档中：

switch 语句类似于同一表达式上的一系列 IF 语句。 在许多情况下，您可能希望将同一个变量（或表达式）与许多不同的值进行比较

当 case 具有常量值时，就像在说 case value == switch value，但是您可以为 case 使用更复杂的表达式。