Need help with script based on conditions

likeglue

I want to write a simple script that evaluates a variable ($num in this case). Depending on what the # is, I want to echo "Less than zero, zero, Between 1 and 10, Between 11 and 20" so on and so on all the way up to "Between 91 and 100, Over 100."

What would I use? An if then statement? A switch statement? What's the easiest way?

Is there some kind of "is between" operator?

Thanks for your help!

We Are 138

LordShryku

Use switch. Anything that evaluates more than three deep (if/elseif/else) should use a switch statement.

likeglue

How would I set up the switch statement then?

laserlight

Actually, since you're testing ranges, a switch is not ideal.

In your case, you could make the range implicit by consistently testing for the lower or upper bound.

if ($num < 0) {
	//negative
} elseif ($num < 10) {
	//0 to 9 inclusive
} elseif ($num < 20) {
	//10 to 19 inclusive
} else {
	//20 or more
}

LordShryku

Well, I tested it, and while the difference is minimal, it does show switch being the winner. I'd say in a case like this, it really doesn't matter though...

<?php
$num   = 101;

$start = microtime();
if ($num < 0) {
} elseif ($num < 10) {
} elseif ($num < 20) {
} elseif ($num < 30) {
} elseif ($num < 40) {
} elseif ($num < 50) {
} elseif ($num < 60) {
} elseif ($num < 70) {
} elseif ($num < 80) {
} elseif ($num < 90) {
} else {
}
$end = microtime();
echo 'If: '.number_format(($end - $start), 6)."\n";

$start = microtime();
switch(TRUE) {
   case ($num < 0):  break;
   case ($num < 10): break;
   case ($num < 20): break;
   case ($num < 30): break;
   case ($num < 40): break;
   case ($num < 50): break;
   case ($num < 60): break;
   case ($num < 70): break;
   case ($num < 80): break;
   case ($num < 90): break;
   default: break;
}
$end = microtime();
echo 'Switch: '.number_format(($end - $start), 6)."\n";
?>

[shryku@blahbox scripts]# php test.php
If: 0.000118
Switch: 0.000083

laserlight

Well, I tested it, and while the difference is minimal, it does show switch being the winner.

My tests using your code show switch being the loser.
In any case, your code gives 10 comparisons for the if-elseif-else structure, and 9 for the switch.

I'd say in a case like this, it really doesn't matter though...

Performance wise, I agree.
But I dont think the switch is appropriate as one would visualise the program flow differently.

likeglue

I tried it and it worked, thanks. I didn't know you can have more than 1 elseif statements. Would there be any advantage or disadvantage of using a switch statement instead?

likeglue

wow, that was fast, sorry I didn't see the other two posts, thanks...

LordShryku

Originally posted by laserlight
My tests using your code show switch being the loser.

Different servers would show different results. It's to be expected.

In any case, your code gives 10 comparisons for the if-elseif-else structure, and 9 for the switch.

I noticed that and changed it to match. It came out at a .000001 difference.

Performance wise, I agree.
But I dont think the switch is appropriate as one would visualise the program flow differently.

And that's opinion. I think switch would be appropriate and would be what I would use.

likeglue

I tried copy and pasting both sets of code into my text file, but neither worked. Is there something else I have to add to the echo statement to actually get it to show up in the browser?

Also, what is the microtime start/end? And I couldn't decipher the last line of the code starting with the echo statement.

Sorry, I'm really new at this (and don't have any programming experience).

We Are 138

Drakla

function what_range($num)
{
	if ($num < 0) return $num . ' is Less than zero';

if ($num == 0 ) return $num . ' is  zero';

$limit = 100;
$range = 10;
$interval = 10;

do
{
	if ($num <= $range)
		return $num . ' is between ' . ($range-$interval+1) . ' and ' . $range;

	$range += $interval;
}
while ($range <= $limit);

return $num . ' is greater than ' . $limit;
}

echo what_range(24);

Raahhh! Think to the future, baby

[EDIT] Thanks to those concerned for not pointing out my 'deliberate' mistake ($range-9)

likeglue

Damn, I don't even recognize any of that stuff from the books I've been studying. Care to dissect exactly what's doing what in that code?

Drakla

No problem, my love. I'll assume you know absoultely nothing, just for fun.

Ok - well to add two strings together you use a dot, full-stop whatever you call it in your chunk of mud, so

echo 'one' . 'two' . 'three'

would output onetwothree. It also works with variables, so if $num was defined to 88,

echo $num . ' is a number';

would output 88 is a number.

Functions can return values - strings, integers, objects, resources - pretty much anything, in the function below I'm returning a string that. You can use echo followed by a function to echo what it returns, hence the echo what_range(24) at the end. Functions can also take arguments in the bracketty bit after the function name, and you refer to them in the function by whatever name you put in

function wahhh($name)
{
	echo 'Hello ' . $name;
}

That function doesn't return anything, but does the printing itself instead.

do / while loops - they do whatever's between the braces { and } while the condition at the end is true - in the case of what_range until $range gets bigger than $limit - so stops when $range goes over 100 in the example

<?php
function what_range($num)
{
		// return a string saying the value is sub-zero
    if ($num < 0) return $num . ' is Less than zero';

	// return a string saying the value is zero (putting $num is pointless here but nevermind)
if ($num == 0 ) return $num . ' is  zero';

$limit = 100;	// when to stop
$range = 10;	// what to start at
$interval = 10; // how big the gaps are between steps

do	// start the loop
{
		// if the number is less than or equal to $range return the value of $range, and its lower limit
		// which is ($range - $interval + 1) eg, if $range at this point is 60, our interval is 15 it would
		// return 56 is between 46 and 60 (range changes every execution of the loop) echo it if you like

	echo 'checking between ', ($range-$interval+1), ' and ', $range, '<br />';

    if ($num <= $range)
        return $num . ' is between ' . ($range-$interval+1) . ' and ' . $range;

    $range += $interval;	// the valud of $interval is added to $range
}
while ($range <= $limit);	// stop if $range is beyond the rim

	// being here means the function didn't return already, so the value is GREATER than our limit, so tell them that

return $num . ' is greater than ' . $limit;
}

echo what_range(24);
?>

Ok, that's enough of that.

likeglue

Awesome, thanks!