Variables Within Regular Expressions

[Anon]

I would like to branch using an if statement if a string is a valid digit of length $length. Here is my line of code:

if(!ereg("^{[[:digit:]]{$length}$",} $value, $matches)) {

That code is not returning the correct response, and I think it's because of my use of $length as the pattern length in the regular expression. What is the correct way to use a variable within a regular expression, as in this case?

[Anon]

You could try breaking this into two pieces:

if(ereg("^{[0-9]$",$value,} $matches) && (strlen($value) == $length)) {
// it's a numeric string of $length characters
}