Checking string contents

[sabien]

I have a form that asks the user for a 6 digit number ranging from 100000 to 999999. Even though it explicitly says it must be a number, someone entered some letters. (i.e. PD0012)

Through my own short-sightedness, I did not put a check for this. I don't know how.

How do I check an input for characters that I deem "illegal"?

[John_Canyon]

$var = "000000";

if(strlen($var) < 6 && !is_numeric($var))
{
die("Please use numbers only.");
}
//else all is great continue

Cheers,

John

[tomhath]

use preg_match for this regular expression.

/\d{6,6}/