如何让这个PHP变量由另一个用户选择的单选按钮的值确定? - How can I get this PHP variable to be determined by the value of another user selected radio button

How can I get this PHP variable to be determined by the value of another user selected radio button

$door = $_POST["doorType"];  
$doorWidth;
if ($door=="Single")
{
        $doorWidth = $width;
}
else if ($door=="Double")
{
$doorWidth = $dOneWidth;
}

当我运行页面时，它不识别变量$doorWidth?

$doorWidth;

没有赋值。它只返回变量…任何事情。PHP这样做就是访问变量，从而产生一个通知。例如:

$doorWidth = NULL; // assigns something (some default value if $door isn't "Signle" nor "Double")

我猜$door的值远低于Single|Double。这可能是由应用程序中的另一个错误引起的。你应该知道，你应该在任何情况下为一个变量设置一个适当的默认值，如果你要分配给它从一个条件语句(如if):

$doorWidth = 'not set!';
if ($door=="Single")
{
    $doorWidth = $width;
}
else if ($door=="Double")
{
    $doorWidth = $dOneWidth;
}

关于switch语句的进一步注意，它有一个default:分支:

switch($door) {
    case 'Single' : 
        // do something
        break;
    case 'Double' :
        // do something else
        break;
    default:
        die('$door has a value far from 'Single|Double'. Currently: ' . $door);
}