if/ else vs. case & speed considerations

[spiggy]

is there any real speed difference between if... else (elseif) and case statements? if it makes any difference im on win2k/ php4.0.5/ apache and generally develop for both linux and windows platforms

also, what is the best way to 'separate' code and html.. if not using templates? and what are the speed issues in this case.

if anyone knows of good (or any) articles in these topics, please share. id like to leave the echo statements behind and i am wondering what would be the best way to do this 🙂

[Anon]

I don't know exactly what you mean by separate code and html, but sometimes when I want to be able to see the html in a wysiwyg editor, what I will do is this:

<?

if($variable){

?>

html html html

<?

} else {

?>

other html other html

<?

}

?>

And thus you can see the html, and it is separated from the code. You can, if need be, just throw in some echo() commands in the html section to show variables changing etc etc.

[Anon]

write some code. people often are saying this is faster then that, this is slower that that. well personal opinion is it depends alot on you hardware/os. write some code. what is more important then someone finding code faster on their machine, is how fast is it on yours. case is slow on my machine.

<?php

class debug
{

function debug()
{
  $this->start = $this->debug_time();
}

function reset()
{
  $all_vars = get_object_vars($this);
  foreach($all_vars as $pos => $val)
    if ($pos != 'error')
      unset($this->$pos);
}

function debug_time()
{
  $time = microtime();
  $time = str_replace('.', '', $time);
  $time = explode(' ', $time);
  $time = $time[1] . $time[0];

  return($time);
}

function time($text = '')
{
  $this->break = $this->debug_time();
  $time = ($this->break - $this->start) / 1000000000;

  error_log(number_format($time, 4) ." : $text \n", 3, '/var/log/php_err.log');

  $this->start = $this->break;
}

}

$debug = new debug;

$debug->time('a');

for($c = 0; $c < 100000; $c++)
if ( $c % 2 )
break;
else
break;

$debug->time('b');

for($c = 0; $c < 100000; $c++)
switch ( $c % 2 )
{
case 0:
break;
case 1:
break;
}

$debug->time('c');

?>

0.0001 : a
0.0002 : b
3.0034 : c

P+133 96mb ram openbsd 2.9

0.0028 : a
0.0047 : b
0.9631 : c

PIII-550 512mb ram Linux 2.2.18

if/else is faster on my P133 but case is aster on my PIII-550 its to hardware dependant.

use this code to check benchmarks.

tail -f /var/log/php_err.log

or wherever your php errors are sent to.

Chris Lee
[e-mail]

[[deleted]]

"P+133 96mb ram openbsd 2.9"
"PIII-550 512mb ram Linux 2.2.18"

"if/else is faster on my P133 but case is faster on my PIII-550 its to hardware dependant"

I should think the fact that you are running two different OS's makes it OS-dependant, not hardware-dependant.

Anyway.

If you use IF and CASE them like this:

switch($var)
{
case 1:
break;

case 2:
break;
}

if ($var==1)
{
};

if ($var==2)
{
};

then case should be faster, because the CASE will stop parsing 'cases' as soon as it matches and comes to the 'break'
The IF statements will all be evaluated because there's nothing to stop that from happening. Yes you could build a nested IF, but that's only for the lucky few who have 25" screens and hawk-vision.

[Anon]

ok to take things out of context. I'll put them back into context

"it depends alot on you hardware/os"

is my quote at the top. the quote at the bottom was implide that the results are hardware/os dependand too not just hardware or os dependent. Im sure OpenBSD vs Linux does make a difference, I am also sure a P+133 and PIII-550 also make a difference. neither on their own, but both together do.

modified if/else

old
0.0001 : a
0.0002 : b
3.0034 : c

new
0.0002 : a
0.0079 : b
3.0013 : c

I supplied the code todo a test. what are the results of your modified if/else ? these are the results of mine on the P133. there is a diff, its marginal.

Im not razing on you vincent but alot of people say this is faster then that, this suck that doesnt. it takes 10sec to do a simple benchmark, it takes even less time to realize is this perf. hit matter to me ?

Chris Lee
[e-mail]

[[deleted]]

Ah, that's clears things up. :-)

It's even more complicated than the pure speed of PHP.
Wether CASE or IF/ELSE is faster depends on more than just raw PHP speed, it also depends on how smart the programmer writes them.
Like I said, if you do 34 sequencial IF statements, it's bound to be slower than a CASE, but if you make a nested IF, it may be faster than the CASE.
On the other hand, if you make the CASE only with function calls, it might be faster still... ah.. the perils of PHP programming...

[Anon]

The code you use has a bug. Using a break in the if-statment will not terminate the the if-block but the for-loop.

Clean code follows and shows to be 10% faster.

#-----------------------------------------
function ifOrCase1() {
for($c=0; $c<10000; $c++) {
$res = $c % 10;
if ($res == 0) {
} elseif ($res == 1) {
} elseif ($res == 2) {
} elseif ($res == 3) {
} elseif ($res == 4) {
} elseif ($res == 5) {
} elseif ($res == 6) {
} elseif ($res == 7) {
} elseif ($res == 8) {
} else {
}
}
}

function ifOrCase2() {
for($c=0; $c<10000; $c++) {
$res = $c % 10;
switch($res) {
case 0: break;
case 1: break;
case 2: break;
case 3: break;
case 4: break;
case 5: break;
case 6: break;
case 7: break;
case 8: break;
default: break;
}
}
}

[Anon]

Case is 10%