case vs. if statements

[jdulberg]

I was just wondering if there is an advantage of using a "case" over an "if" statement?

I'm doing a query on a database that contains a user level of 0 to 4. In the header, I'd like to display some text depending on what user level the person is. So would this be a job for an "if" statement or a "case" statement?

Any insight is appreciated.

[Defender1]

a case is pretty much the same.
though it's a little more effecient when you want to run a lot of if's or elseif's in sucession.

[kunal]

well... case is easier then if when reading the code.. atleast for me.. it makes the code much cleaner.. and easier to debug... all the curly brackets in the if statement can get a lil confusing..

[Defender1]

yea, it's easy to misplace a bracket.

[alexk]

with relation to performance, it's all the same (at least it used to be like that in C++)... so just use what you like more

i normally use case for 4+ cases %)

[Michel V]

I use it for multi-purpose PHP files, like switch($action) and case "update", case "edit", etc
It's a very efficient way to group multiple PHP files into just one.

But for casual if statements, like 1 to 4 or 5 choices, I'd stick to if.

[Skunk]

I'd be surprised if there was a speed advantage for one method over the other - it's all a case of personal preference really. Case is handy if there are lots of possible options and each requires different logic. For example, most of the scripts I write use an $action variable (set in the query string) to tell the script what to do. I can quickly and easily structure the script with a switch statement:

<?php
switch ($action) {

case 'addnews':
    // Code for adding news
    exit;

case 'editnews':
    // Code for editing news
    exit;

case 'search':
    // Code for the search facility
    exit;

case 'archive':
    // Code for news archive
    exit;

default:
    // Code for if no action is specified, or action didn't match the above

?>

Another handy attribute of switch is the fact that program execution can "fall through" to the next case statement if you don't include an exit or break. I've never had a reason to use this but I can imagine it could save a lot of time in some situations.

[freddydoesphp]

Just cause I was curious I ran an apache benchmark test on two files one using if elseif and once using switch() here are the results:

test1.php

<?php
$action = "addnews";
switch ($action) {

case 'addnews':
    print "addnews";
    // Code for adding news
    exit;

case 'editnews':
    print "editnews";
    // Code for editing news
    exit;

case 'search':
    print "search";
    // Code for the search facility
    exit;

case 'archive':
    print "archive";
    // Code for news archive
    exit;

default:
    print "default";
    // Code for if no action is specified, or action didn't match the above
    }
?>

test2.php

<?php
$action = "addnews";

if($action == 'addnews') {
    print "addnews";
    // Code for adding news
    }
elseif ($action == 'editnews') {
    print "editnews";
    // Code for editing news
    }

elseif ($action == 'search') {
    print "search";
    // Code for the search facility
    }

elseif ($action == 'archive') {
    print "archive";
    // Code for news archive
    }

else {
    print "default";
    // Code for if no action is specified, or action didn't match the above
    }
?>

Results for test1.php

Server Software:        Apache/1.3.12                                      
Server Hostname:        www.domain.com
Server Port:            80

Document Path:          /test1.php
Document Length:        7 bytes

Concurrency Level:      100
Time taken for tests:   1.611 seconds
Complete requests:      1000
Failed requests:        0
Total transferred:      254762 bytes
HTML transferred:       7021 bytes
Requests per second:    620.73
Transfer rate:          158.14 kb/s received

Connnection Times (ms)
              min   avg   max
Connect:        0     2    10
Processing:    14   149   283
Total:         14   151   293

Results for test2.php

Server Software:        Apache/1.3.12                                      
Server Hostname:        www.domain.com
Server Port:            80

Document Path:          /test2.php
Document Length:        7 bytes

Concurrency Level:      100
Time taken for tests:   1.622 seconds
Complete requests:      1000
Failed requests:        0
Total transferred:      254762 bytes
HTML transferred:       7021 bytes
Requests per second:    616.52
Transfer rate:          157.07 kb/s received

Connnection Times (ms)
              min   avg   max
Connect:        0     3    12
Processing:    14   149   159
Total:         14   152   171

As you can see the results are so minimal that I think Skunk hit the nail on the head, and it all boils down to personal preference.

[Abstraction]

The way I see it is the case is less typing and more readable than the if/else.

[freddydoesphp]

Less typing and more readable doesn't mean better, for you personally its better, but the tests don't lie, and there is no reason to change anything if you happen to use if/elseif. There isn't enough of a difference.

[Abstraction]

Originally posted by freddydoesphp
Less typing and more readable doesn't mean better, for you personally its better, but the tests don't lie, and there is no reason to change anything if you happen to use if/elseif. There isn't enough of a difference.

I never said one was better than the other or that one should go and change their code. ;-)

[alexk]

freddydoesphp, I'm just curious about the results of above tests with
$action = "default";

[jdulberg]

Wow... thanks for all your comments.... I didn't expect this much attention to the question.

I ended up using a case statement - since it appears that speed isn't a factor between the two methods, I felt like trying something different... I've never used the case before so this is my first.

Thanks to everyone for all your comments!

[freakysid]

Well I agree that efficiency of execution is *not* a significant concern 80% of time (results of independent research conducted at the freaky laboratories). However, well written code is self documenting code. This includes things like giving variables meaningful names that relate the the data they represent. It also means chosing the appropriate control structure that best represents the type of logic you, the programmer, have in mind.

For example, there several ways you could iterate through an array that are all technically feasable:
Example 1: the traditional approach to traversing an array in many languages

$myArray = {0, 1, 2, 3, 4, 5};
$count =  count($myArray);
for($i = 0; $i < $count; $ i++) {
   echo $myArray[$i];
} 

Example 2: technically valid but more obscure way of doing the same thing (harder to glean the logic on first reading).

$myArray = {0, 1, 2, 3, 4, 5};
while(! empty($myArray[$i])) {
   echo $myArray[$i++];
} 

But the cleanest, most lucid way of writing this (IMHO) because it is self documenting (the code clearly explains the programmers thinking):

$myArray = {0, 1, 2, 3, 4, 5};
foreach($myArray AS $element) {
   echo $element;
} 

As others have stated already, on top of the fact that it is easier to format and read a switch structure over a long if/elseif/else stucture. However, the point I was getting at with my code above is that there are times when the switch control structure illustrates the purpose of the code and the architecture of the script. Skunk's example is the classic example of creating a switchboard architecture. See http://www.fusebox.org/. They call their architecture fusebox, but I think that the metaphore of a switchboard is more suitable. I have been working on a member control panel for a site and the switchboard architecture is perfect for this. Here is a pseudo-mumbo-jumbo explaination (hehe - the last time I wrote pseudo-mumbo-jumbo, no one understood what I was going on about):

IF the user's session is not valid THEN
   redirect user to login page
   EXIT the script
END IF

include the file with the member control panel header and navigation html

SWITCH ON HTTP_GET_VARS[action]
   CASE OF "foo"
      include file "dofoo.php"
      break
   CASE OF "bar"
      include file "dobar.php"
      break
   DEFAULT ACTION
      include file "default.php"
END SWITCH

include the file with the member contol panel footer html
EXIT

So hopefully not only is the code I would write to impliment that design neat and readable, but it reflects the architecture of the member control panel application. The control panel pages are generated by sending all requests through a index.php which acts as a switchboard. The designer can also, hopefully, follow the logic of the application and see how his/her client side code will fit in. So hopefully it is a clean architecture for all parties to follow.