[RESOLVED] > or < ZERO

[partypete]

Hello,

Bit confused here. Let's say I want to validate that a person is submitting a whole-number from ZERO to infinity...

I can validate that the submitted number is greater/equal-to 1 like this:

$v = "5";
if($v >= 1){
echo "Pass";
}

Two things I'm confused about...
1) How to make sure it's a whole number, ie: 2 or 3, not 2.5
2) How to deal with zeros.

When dealing with zeros, both of the following "Pass" even though $v is a word, not a number:

$v = 'word';
if($v >= 0){
echo "Pass";
}
if($v >= '0'){
echo "Pass";
}

To me, one of the above seems like it should look for the number zero or a greater number but they don't. They both echo "Pass".

How do you validate a number so as to make sure it is a whole-number ranging from 0 to infinity??? Oh, and also to make sure that an empty variable "" is not interpreted as a zero.

THANKS!

[Installer]

One way to do it:

if ((strlen($a) > 0) && ctype_digit($a) && ($a >= 0))

[partypete]

Thanks Installer. That should work great. Nice to also learn about the other ctype_ functions.

[Weedpacket]

or

if(is_numeric($v) && $v>=0) { pass}

[Installer]

"is_numeric()" returns true given a non-integer (e.g. 1.5).

In the solution I posted the third test ($a >= 0) isn't really needed since the second test (ctype_digit($a)) will return false if the input contains a minus sign.

[Weedpacket]

Oh, yes; a whole number. I guess intval(abs($v))==$v is going a bit far then. It would also fail on 2837462785675761454546475825667254724.

Hah! There's the solution!

if(preg_match('/^[0-9]+$/', $v))

Assuming 000000000000000000000042 counts as a whole number.

if(preg_match('/^(0|[1-9][0-9]*)$/', $v))

if it doesn't.
Yes, I'm avoiding ctype_digit.

[partypete]

Thanks both for your help. Hey Weedpacket, you're avoiding ctype_digit for fun right? or is there an actual reason you don't like using it?... just to be clear. :-D

[Installer]

Since the pregs don't seem to work, and since the input may not always be a string, here's another revision that should work with either string or numeric input (and it uses both "$v" and "$a", as well as "ctype_digit()"):

if ((strlen($v = (string) $a) > 0) && ctype_digit($v))

[partypete]

Hey Installer, could you explain this part:

strlen($v = (string) $a)

Sorry that I have to ask, but there's no way to look these things up on php.net.

I understand the simpler version... strlen($v), but I'm not sure what it is you're doing with...

$v = (string) $a

Thanks yet again.

[Installer]

Every assignment has a return value, and this one will return a string type which can then be used with both the greater than comparison and the ctype function. It's equivalent to:

$v = (string) $a;
if ((strlen($v) > 0) && ctype_digit($v))

and the same results can be gotten with:

$a = (string) $a;
if ((strlen($a) > 0) && ctype_digit($a))

or:

if ((strlen((string) $a) > 0) && ctype_digit((string) $a))

[Weedpacket]

Partly for fun, partly because ctype_digit's definition of "digit" depends on what locale you're configured for (which is also why I didn't use \d instead of [0-9] in preg_match), partly because ctype_digit(120) != ctype_digit('120') and that sort of thing annoys me a bit, partly because I'm using preg_match() often enough for other patterns that it's just more familiar (a lot easier, for example, to later modify the preg_match() pattern to allow negative numbers, should the need arise).

Dunno what Installer means by "the pregs don't seem to work" - there's not enough to them to go wrong, and they work for me - but $v=(string)$a is covered here (Under "Language/Types".) It's converting the value of $a into a string and putting the result in $v. Half-pointless in this case, because the argument to strlen() is converted to a string anyway.

[Installer]

My apologies, Weedpacket. The pregs do work very well. It was faulty testing on my part, which I hope not to happen again. You used regular expressions to come up with two solutions quickly while I was floundering about.

Yes, the conversion to string (for "strlen()")is half-pointless and a bit too far. I tried to point out the other half in my post, either unsuccessfully or unacceptably, I guess. In any case I still believe that reading, testing, and adapting code is a good part of learning to program, so maybe I was able to help.

[Weedpacket]

Not a problem; two perspectives for the price of one ain't a bad bargain.

(...when I was growing up we didn't have these fancy ctype_* functions. We had to do all our character matching with regexps. In the snow. And we didn't have those PCRE ones either - we had to use POSIX. Hoowhee, I remember when we got our first PCRE engine. All the neighbourhood came 'round to see it. Mind you, that was back in '01 before the Depression hit....)