Validating field to contain only numbers separated by commas

Question

I'm making a form validation callback in code igniter. I'm trying to validate an input that needs to be numbers separated by commas, no spaces. For example

1,2,3,4,5 221,78,4,82,991,12 10001,10010,20010 etc

Whats the best way to validate this regex? Some other PHP wizardry?

Answer 1

Here's an expression that won't require any backtracking.

/^(?:\d+(?:,|$))+$/

The non-capturing groups (?:regex) also make it faster.

Answer 2

Why not a regex like this?

/^(\d+,)*\d+$/