[SOLVED] Simple code (switch/case) working 87% of the time

[VarHyid]

Hi, all

 

First off, it's a SOLVED problem which a) still keeps me thinking, but b) requires a question for the future. I'm actually still learning (by doing) PHP so maybe there's a simple reason for this case, in which case - sorry for bothering

 

I'm writing a very simple script that displays 1 of 4 possible events depending on a number in a (MySQL) database. It's really basic.

 

$ttest = $usrfield['ttest'];

switch ($ttest) {
case ($ttest < 50):
	$ttestr = "<div>Get at least 50 credits</div>";
	break;
case ($ttest > 49 && $ttest < 500):
	$ttestr = "<div><b>RANK 1</b></div><div style='color: #d00000; font-size: 10px;'>You have <b>".$ttest."</b> credits</div>";
	break;
case ($ttest >= 500 && $ttest < 5000):
	$ttestr = "<div><b>RANK 2</b></div><div style='color: #d00000; font-size: 10px;'>You have <b>".$ttest."</b> credits</div>";
	break;
case ($ttest >= 5000):
	$ttestr = "<div><b>RANK 3</b></div><div style='color: #d00000; font-size: 10px;'>You have <b>".$ttest."</b> credits</div>";
	break;
}

 

As I said - very basic. There are 15 (almost) EXACT codes, varying by the variable name (for example: $rtest + $rtestr, $ptest + $ptestr and so on) which make a document included in the "main" file which echoes all of them $ptestr, $rtestr, $ttestr etc.

 

The main document also sets

 

$usrfield = mysql_fetch_assoc($resultusr);

 

and $resultusr is a mysql_query selecting a particular user's row with ptest, rtest, ttest... named columns.

 

Here's the funny thing - it works perfectly in 13 out of 15 cases. In 2 cases, where the number is 0 it doesn't display "Get at least 50 credits", but returns "RANK 1..." instead (with 0 within the text). And it's not like these are the only two zeros - there are a 4 more and all 4 work fine and return "Get at least 50 credits".

 

I've been staring at the complete code half an hour, copying/pasting the working part that displays 0 properly and mass-replace "rtest" to "ttest" (for example) and still nothing. I've tried to check/repair the particular MySQL table - PhpMyAdmin says it's OK. All fields have same properties, all are 0-default, decimal(6,0). I've tried to make a separate case for $ttest equaling 0 and one for it being less than 50 and then 0 worked, but... nothing else, still returned 0-case even with 45671.

 

Then I've separated the first case and made an if (case1) else (switch):

 

$ttest = $usrfield['ttest'];

if ($ttest < 50) {
$ttestr = "<div>Get at least 50 credits</div>";
}
else {
switch ($ttest) {
	case ($ttest > 49 && $ttest < 500):
		$ttestr = "<div><b>RANK 1</b></div><div style='color: #d00000; font-size: 10px;'>You have <b>".$ttest."</b> credits</div>";
		break;
	case ($ttest >= 500 && $ttest < 5000):
		$ttestr = "<div><b>RANK 2</b></div><div style='color: #d00000; font-size: 10px;'>You have <b>".$ttest."</b> credits</div>";
		break;
	case ($ttest >= 5000):
		$ttestr = "<div><b>RANK 3</b></div><div style='color: #d00000; font-size: 10px;'>You have <b>".$ttest."</b> credits</div>";
		break;
}
}

 

and surprise, surprise - it works

 

So here's the question - is there something special about the 0 or about switch that it doesn't always work or only with particular numbers ( )? Should I always mix if/else with switch in some particular situations? Or maybe ditch the switch completely and make it an if/elseif for... whatever reason?

[ngreenwood6]

I would replace you switch stament with an if/elseif/else block. Switch statements more or less are just used to test specific values that you know can come of that. So it would be something like this:

 

<?php
$dog = 'johnny';

switch($dog){
  case 'johnny':
    echo $dog;
    break;
  case 'another':
    echo 'not'.$johnny;
    break;
}

 

The only time I use switch is if I am checking against values that I know it will be. Hopefully that will help.

[VarHyid]

OK so no more switches to variables to variables to variables to queries to variables...

 

Thanks, will make ifelse's just in case.

 

Still, out of curiosity, any idea why it worked in all 13 out of 15 cases?

[Alex]

Normally a switch statement can not be used with multiple conditions, although it can be 'hijacked' to work like this, it's usually not a good idea. Here's why it's not working.. A switch statement compares the value in it's parameter to each case, if it's true then that case fires. Because you're usnig $ttest it compares (for example) $ttest to $ttest > 49 && $ttest < 50. The statement '$ttest > 49 && $ttest < 50' will evaluate to either true, or false. You want the case to fire if it's true. But when $ttest is 0 it's basically trying to compare false (because 0 == false) to the statement, giving you the exact opposite of what you want. Here's what happens:

 

$ttest = 0;
switch ($ttest) {
case ($ttest < 50): // $ttest < 50 evaluates to true, but you're comparing this true, to $ttest, and since $ttest == 0 == false you're getting: true != false so it goes to the next statement..
	$ttestr = "<div>Get at least 50 credits</div>";
	break;
case ($ttest > 49 && $ttest < 500): // Here you're getting false for '$ttest > 49 && $ttest < 500' and $ttest is == 0 == false, of course, false == false. which is why this one is triggering.
	$ttestr = "<div><b>RANK 1</b></div><div style='color: #d00000; font-size: 10px;'>You have <b>".$ttest."</b> credits</div>";
	break;
case ($ttest >= 500 && $ttest < 5000):
	$ttestr = "<div><b>RANK 2</b></div><div style='color: #d00000; font-size: 10px;'>You have <b>".$ttest."</b> credits</div>";
	break;
case ($ttest >= 5000):
	$ttestr = "<div><b>RANK 3</b></div><div style='color: #d00000; font-size: 10px;'>You have <b>".$ttest."</b> credits</div>";
	break;
}

 

Long story short, you can just use switch(true){...} instead of switch($ttest){...} to get the functionality that you're looking for. Although, I'd go for an if.. else if.

[VarHyid]

Oh. Now it actually makes sense. Many thanks.

 

I'll go with if/elseif/eslseif/else.