default as first option in switch statement?

Question

I\'ve tested this and it works fine, but it looks... weird... to me. Should I be concerned that this is nonstandard form which will be dropped in a future version of PHP, or

Answer 1

Other answers give good examples of it, just stating for clarity's sake...

A Case (including default) does not stop executing at its end unless you include a break. Although switch is often compared to a sequence of if elseif elseif etc., however it's not quite that.

Short version: SWITCH/CASE only acts like IF/ELSEIF/ELSE if you include breaks after each case. SWITCH/CASE is more like a series of "if" statements where each has the same variable check with a different value it's being checked against.

Long version: Without including a break, each case is a "start here"and the differences in a lot of ways make it closer to GOTO without the drawbacks. Technically, if you really REALLY wanted to (read, were a masochistic coder who wanted to really challenge themselves) you could write almost any procedural programs using only one external array, a for loop, and a switch nested inside.

Seriously, why you would want to do this boggles my mind, but it really demonstrates how far switch/case can deviate from if/elseif patterns, so it's here for you for academic reasons (but don't do it!)...

$array = [];
$array['masterLoop'] = 1;
$for ($i = 0, $i < $array['masterLoop'], $i++ ){
    switch($array['goto']){
        default: 
        case 1: 
            PRINT: "Welcome to the program";
        case 2: 
            PRINT: "Please make a choice:";
        case 3:
            $array['choice']='';
            // Wait for some input variable and set choice to it.
        case 4: 
            $array['goto']=$array['choice'];
            $array['masterLoop']++;
    }
}

The way this code would run (after you set up something for capturing and setting a choice) would be it'd start up with

"Welcome to the program. Please make a choice."
<<user inputs 2>>
"Please make a choice."
<<user inputs 1>>
"Welcome to the program. Please make a choice."
<<user inputs 3>>
// program awaits user input
<<user inputs 4>>
// user triggers infinite loop

So... you can use switches to reflect back to the days of BASIC... but if you do and I have to debug your code later after you wrote it all like that... May Linus Torvalds mercy on your soul.

Answer 2

It is an unusual idiom, it causes a little pause when you're reading it, a moment of "huh?". It works, but most people would probably expect to find the default case at the end:

switch($kind)
{
    case 'kind2':
        // do some stuff for kind2 here
        break;

    // [...]

    case 'kindn':
        // do some stuff for kindn here
        break;

    case 'kind1':
    default: 
        // Assume kind1
        $kind = 'kind1';

        break;

}

Answer 3

In case anybody find this page through google as I did:

I was wondering the same thing as Josh - so... One thing is standards, which I think we should all try harder to adhere too, but another thing is hacking (in the: exploit-every-possibility kinda way).

While it's ugly/weird/not normal - it IS possible and IMHO could be useful in some rare cases...

Consider the following:

$color = "greenish";
//$color = "green";

switch($color) {
    default:
        echo "no colors were selected so the color is: ";
    case "red":
        echo "red<br />\n";
        break;
    case "blue":
        echo "blue<br />\n";
        break;
    case "green":
        echo "green<br />\n";
        break;
}

If $color = "greenish"; the code will print

no colors were selected so the color is red

while if $color = "green"; or any other defined cases, it will just print the color.

It know it not the best example, but you get the point ;) Hope it helps somebody.

Answer 4

This is how I'd probably do it... it's easy on the eye and keeps the functionality.

switch($kind)
{
    case 'kind1': default :
        // Do some stuff for kind 1 here
        break;
    case 'kind2':
        // do some stuff for kind2 here
        break;
    case 'kindn':
        // do some stuff for kindn here
        break;
}

Answer 5

Common practice is to define the default option as last option. But I see nothing wrong with your solution (if there is no predefined schema in your company how to layout your code)

Answer 6

Kind of made me twinge at first, but that's just because we're not use to seeing things that way.

I would suggest that you document this highly, since some might call this "tricky" code. A noob or some future maintainer might come along and move it to the bottom where they're more comfortable with it and break the side-effect that is has being at the top.