[RESOLVED] Comparison operators doesnt work

Bizcut1

Because I'm not that good at English, I couldn't find a better title for this thread.

But here we go: My problem is that the comparison operators fail in some situations.

I've got an input field where the visitors enter a number. I have limited the size of the number to 10 000 by doing the following:

if ($value <= "10000") {
//continue
} else {
//error output
}

The $value is correct, and there is nothing wrong with the code. The limit does work. But if the visitor types in a 601-digit long number in the input field, it goes right through the $value-limit. How is this possible? Any other value doesn't have this problem, but with 601-digit number(maybe with bigger numbers also) it gets through.

Is this a common bug in PHP?

Piranha

Why do you think it is a bug in PHP?

Do you have any proof that it is a bug?

Strange that it is not solved in case it is a bug, more persons than you mush have seen it.

On the other hand, if it is your code and not a bug I can't understand why you blame PHP. It will most likely result in these kinds of answers.

A good start for you would be this.

Bizcut1

I'm not saying that this is a bug, I am ASKING. I'm sorry if you misunderstod me.

In my opinion the coding can't be wrong, it is very straight-forward. Nothing complicated. And when it only fails on such big numbers, it it is unlikely that there is anything wrong with the coding.

NogDog

The max size for an integer in PHP (assuming a 32-bit signed integer) is 2,147,483,648. If you try to use anything larger in arithmetic operations or comparisons, it will generate unexpected results due to overflowing the 32-bit memory for that integer. You might want to try something like:

$value = trim($_POST['value']);
if(ctype_digit($value) and strlen($value) < 6 and $value <= 10000)
{
   // continue
}
else
{
   // error
}

This will ensure that $value is an integer and of a safe number of digits that it won't overflow before checking that it is in the correct numeric range.

Bizcut1

NogDog: Thank you very much. That solved my problem.

bpat1434

If you're using an input field for people to input numbers (anything below 10,000) you might want to use the [man]intval/man function to get the integer value of the string(s) you want to compare.

if(intval($value) <= 10000) {
    // continue ...
} else {
    // Don't continue ...
}

But that will only work if you are using numbers. If you're using text, you'd be better off using [man]strcmp[/man] or [man]strnatcmp[/man] which will compare strings.

EDIT: DARN YOU CHARLES!!! Beat me to it...

Piranha

Sorry to nag about it, but this is exactly what I ment:

Bizcut1 wrote:
In my opinion the coding can't be wrong, it is very straight-forward. Nothing complicated. And when it only fails on such big numbers, it it is unlikely that there is anything wrong with the coding.

You just assume that your code is perfect and that someone else screwed up.

Oh well, I'll stop nagging about it now, don't want it to become a flame war.