[RESOLVED] Since when is 0 between 8 and 15 ?

[The_Chancer]

This little snippet should set the $bg color of a table row to be according to the following :

switch($info2['port'])
                {
                  case($info2['port']>=0 && $info2['port']<=7):
                    $bg = "red";
                    break;
                  case($info2['port']>=8 && $info2['port']<=15):
                    $bg = "green";
                    break;
                  case($info2['port']>=16 && $info2['port']<=23):
                    $bg = "lightblue";
                    break;
                  case($info2['port']>=24 && $info2['port']<=31):
                  $bg = "yellow";
                  break;
                }

And considering that $info2['port'] is 0 in this case, why would the following be given out ?

<tr bgcolor='green'><font color='white'><td>500226</td><td>*****</td><td>CLI HERE</td><td></td><td>Exchange</td><td>(frame)0</td><td>(slot)25</td><td>(port)0</td><td>(incident)</td><td>(Ring)Neos Direct</td></font></tr>

The $info2 array is set by mysql_fetch_assoc which populates the data in the table, frame,slot and port are set as type INT in the database.

If anyone knows why 0 would appear between 8 and 15 and not any others, please let me know... (or point out any idiotic mistakes... I'm open to comment/slating/laughing)

Thanks,

[ahundiak]

Might want to read up on the switch statement:
http://www.php.net/manual/en/control-structures.switch.php

It only does a simple value comparison. Use a set of if statements or maybe an array.

[The_Chancer]

I did - and the first line i read was "The switch statement is similar to a series of IF statements on the same expression"

Surely the use of a set of if statements would be covered by that line alone...

[The_Chancer]

It seems as though it is possible - by not switching on ($info2['port']) but on (TRUE) instead.

switch(TRUE)
{
  case($i>=0 && $i<=7):
    $bg = "red";
    break;
  case($i>=8 && $i<=15):
    $bg = "green";
    break;
  case($i>=16 && $i<=23):
    $bg = "lightblue";
    break;
  case($i>=24 && $i<=31):
    $bg = "yellow";
    break;
}

Now works...

[bradgrafelman]

If I understand the logic correctly, the reason your previous code didn't work is because the part inside the switch() command is evaluated against each case, so it's basically as if you're saying:

if($info2['port'] == ($info2['port']>=8 && $info2['port']<=15)) { ... }

Now, since PHP is a weakly-typed language, and since the second part of that comparison is false, PHP probably evaluated $info2['port'] as FALSE (since FALSE == 0 == FALSE), which makes that if() statement true:

if(FALSE == ($info2['port']>=8 && $info2['port']<=15)) { .. }
// since $info2['port'] isn't in that range, the right side is FALSE, leaving:
if(FALSE == (FALSE)) { ... }

Doing a switch(true), however, would work, since you're trying to see which expression in the case statements == TRUE.

[scrupul0us]

you might also want to use w3c compliant styling in your code:

instead of:

<tr bgcolor='green'><font color='white'>

use:

<tr style="background-color: green; color:white;">

caution that not all browsers render styling to a TR tag... might want to wrap things in DIV's

but i digress 😉

[Weedpacket]

bradgrafelman wrote:

Doing a switch(true), however, would work, since you're trying to see which expression in the case statements == TRUE.

By which point, of course, you're just back to a series of if statements. Which, incidentally, would mean less code. Not only is there the spurious switch() that doesn't actually do anything anymore, but the tests themselves can be simplified.

if($info2['port']>=0) {
	if($info2['port']<8) $bg='red';
	elseif($info2['port']<16) $bg='green';
	elseif($info2['port']<24) $bg='lightblue';
	elseif($info2['port']<32) $bg='yellow';
}

Because once you've decided that it's (a) at least 0, and (b), not less than 8, then you can safely conclude that it is at least 8 without having to explicitly check that such is indeed the case.

[bradgrafelman]

What's more, haven't benchmarks shown that the if() statements are slightly faster than a switch() ?