在PHP中切换case语句

Question

I am learning PHP. I have downloaded an open source project from a website and looking the workflow of each modules in that project. I noticed a switch case which is unfamiliar to me.

switch ($value) {
        case 'student':
        case StudentClass::getInstance()->getId();
            return new StudentClass();
            break;
        case 'teacher':
        case TeacherClass::getInstance()->getId();
            return new TeacherClass();
            break;
        default:
            break;
    }

The above patch is what I looked. When I give input:

$value = 'student';

It returns StudentClass instance.

If I give

$value = 'teacher';

then it returns TeacherClass instance.

If anyone explain the flow, it will be helpful to me to understanding PHP much better

Answer 1

Your string cases don't have break or return statements, so they "fall through" to the next case. Also, your breaks don't serve any purpose here.

I've added comments to your code to explain what's happening.

switch ($value) {
        case 'student': // keeps going with next line
        case StudentClass::getInstance()->getId();
            return new StudentClass(); // handles both cases above
            break; // unnecessary because of the return above
        case 'teacher': // keeps going with next line
        case TeacherClass::getInstance()->getId();
            return new TeacherClass(); // handles both cases above
            break; // unnecessary because of the return above
        default:
            break; // pointless, but handles anything not already handled
}

Also, PHP explicitly allows use of a semicolon (;) after a case, but it is not generally considered good style. From the docs:

It's possible to use a semicolon instead of a colon after a case...