OK,

I needed to to be able to validate a zero value (0) or a valid integer with a max length of 11 digits for a parent_id field in a nested table (like com_categories table) that I'm working on...

This is how:
How it works:

• The outer parentheses '()' allow separate arguments
• The pipe '|' denotes an OR statement
• Square brackets denote acceptable characters
• Curly braces '{val1, val2}' specify, upper (val2) and lower (val1) length

So, this regex basically says,

1. IF the first character matches anything between 0 and 9 ([0-9]) and is only 1 digit long ({1,1}) OR (|)
2. IF the first character matches anything between 1 and 9 ([1-9]) AND any subsequent characters are between 0 and 9 to a total length of 10 and a minimum of 1 then... RETURN TRUE

ELSE

RETURN FALSE

**N.B.We only check for a length of 10 as we are only checking everything after the first character in the second case. There are 11 in total - the maximum length of ID fields in the DB**

Hope this Helps!!!

Gez

audibleid wrote: Shortens to by removing extra parentheses & {1,1}:Gez

Yes, that would work, but it simplifies even more:
or