What does this preg_match syntax match ".+?"

Question

I know perl style regular expresions fairly well, but today I found one that I do not understand:

preg_match('/^On.+?wrote:.+?$/i',$line); //reduced example

What does the .+? mean? I undarstand the .+ alone, I understand .? alone. But .+?? It seems a bug to me.

The line should match popular citation prefixes in the email body and it is much more complicated along with look behinds, but this is the only part i can't understand, and still the regexp seems to work correclty.

See also [stackoverflow.com/questions/13705478](http://stackoverflow.com/questions/13705478/what-is-the-difference-between-the-regex-and/13705682#13705682) — stema, Apr 01 '14 at 09:37

score 2 · Accepted Answer · answered Apr 01 '14 at 08:52

2

+ means one or more and is greedy. +? means the same, it just is not greedy like usual regex are.

Edit: I wanted to explain it a little further, but the comment of deceze already explains enough.^^

answered Apr 01 '14 at 08:52

Realitätsverlust

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That simple. Face palm. I should have known that... Thank you :-) – SWilk Apr 01 '14 at 08:54
@SWilk regex are pretty complicated, i don't think its a reason to facepalm just because you didn't recognize a syntax immediately. I got my regex cheatsheet next to me all time because i always forget something. :) – Realitätsverlust Apr 01 '14 at 08:56
Yeah, but I was "our local regexp guru" at the office. And I have used much more advanced and unreadable features. And now I have stumbled upon some basic ungreedeness. Nothing happend, just some ego injured ;) – SWilk Apr 01 '14 at 09:05

score 2 · Answer 2 · answered Apr 01 '14 at 08:53

In short, when you add ? its matching least amount possible, where as without ? its matching most amount possible:

Here is the explanation:

NODE                     EXPLANATION
--------------------------------------------------------------------------------
  .+?                      any character except \n (1 or more times
                           (matching the least amount possible))
--------------------------------------------------------------------------------
  .+                       any character except \n (1 or more times
                           (matching the most amount possible))

score 0 · Answer 3 · answered Apr 01 '14 at 08:54

0

Lazy not Greedy

.+? matches any character (except newline)

Quantifier: Between one and unlimited times, as few times as possible, expanding as needed [lazy]

check at regex101.com

answered Apr 01 '14 at 08:54

pawel7318

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Wheres the difference? Lazy and not greedy actually mean the same. They only take as much as they need to fulfill the condition. – Realitätsverlust Apr 01 '14 at 09:09
I mean it's **Lazy** `.+?` instead of **Greedy** `.+` – pawel7318 Apr 01 '14 at 09:14
Oh. Well, that's right. Sorry, it was a long day, i have lost my ability to think. :D – Realitätsverlust Apr 01 '14 at 09:20

What does this preg_match syntax match ".+?"

3 Answers3