Question

Valid, and ONLY possible source string formats: (numbers and letters will vary)

1. xxxx/xxxx/0884/11 (x corresponds to random letters)
2. xxxx/xxxx/884/11   (x corresponds to random letters)
3. 884/11
4. 0884/11
5. 7/11

Desired outputs after extraction (respectively):

1. 0884
2. 0884
3. 0884
4. 0884
5. 0007

Can this be done a bit cleanly, with perhaps some regex?

Answer 1

Blah 🙂 the generic condition is: (beginning of string OR characters than /) and after that 1 to 4 numbers, the precondition in PCRE is: ^|\w+/, numbers are: \d{1,4}.

Joined together you will get this regexp: ~(^|\w+/)(\d{1,4})~ which can be used with preg_match() into this:

$match = array();
preg_match( '~(^|\w+/)(\d{1,4})~', $yourLine, $match);
// And pad it to left side with zeros:
$result = str_pad( $match[2], 4, '0', STR_PAD_LEFT);