newb regEx question

vvuiverine2

In the following example why does the first echo statement print true and the second false?

$string = "123456789";

echo preg_match("/\d{1,5}/",$string)
echo preg_match("/\d{,5}/",$string)

From what I've read the first states atleast 1 but no more than 5 decimal chars. The second, atleast 5 decimal chars.

What am I missing here?

toplay

First of all, it doesn't usually return a boolean value but an integer of how many times it matched. It returns FALSE only on an error (like when you supply a bad expression).

The "{,5}" part is not valid syntax. Since it's the wrong syntax, it's taken as a literal and it will actually look for that exact literal and hence why it can't find a match. If you want it to be exactly five times then use "{5}" syntax instead.

🙂

vvuiverine2

Okay, so the first statement echoes 1 or 0 depending on whether a match was found.

How come the first expression matches?

thanks for the response.

toplay

The first expression matches because it finds "12345". You're asking it to find at least one numeric digit but up to five.

If you used preg_match_all() instead, it would make a match on "12345" and then again on "6789".

If you used '/\d{1,5}?/' expression instead, then that would match the least number of digits each time. The question mark makes it lazy (match as few as possible up to 1 in this instance). Without the question mark it's greedy (match as many as possible up to 5 in this instance).

FYI: Link # 9 under "Regex/PCRE:" in my signature is to a nifty program well worth the $30 price tag.

vvuiverine2

Thanks, it now makes a whole lot of sense to me.

My book has a poor description of the min/max quantifiers.

toplay

You're welcome. Look at the links in my signature line for tutorials and links to web sites for testing your expression online!

Happy coding.

🙂