Check if a variable is a natural number

Question

I want to make a bid system on a website. That means users can post their bid (natural number). I want to make sure users don't try to post characters, decimal numbers, etc. I don't want to use is_numeric function because hexadecimal notation is allowed. I was thinking to use preg_match for this. But in php.net the documentation for this function is little and I have no idea how to use preg_match.

So how should I check if a variable is a natural number with preg_match?

Answer 1

If you don't require decimal points: ctype_digit or filter_var($var, FILTER_VALIDATE_INT).
If you do: filter_var($var, FILTER_VALIDATE_FLOAT).

Answer 2

ctype_digit does what you want:

Checks if all of the characters in the provided string, text, are numerical.

(Before PHP 5.1.0, this function returned TRUE when text was an empty string.)