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Question

php regex for string containing a "." and "-"

Answer 1

+13 A:

You don't need a regex for that:

if (strpos($string, '-') !== false && strpos($string, '.') === false)
    //do what you want...

Franz 2009-11-10 09:47:28

strpos() is more efficient than regex matches, especially in cases like this. This is the perfect answer. +1

Duroth 2009-11-10 09:58:03

strpos has to scan the string twice, a good regexp only once!

reto 2009-11-10 10:02:33

@reto: True. Would have to run a benchmark to havee the "real" comparison. But in a simple case like this it probably does not matter, I think... Do you agree?

Franz 2009-11-10 10:06:53

@Duroth: Efficiency and performance are not the same.

Gumbo 2009-11-10 10:11:26

Franz: I dont really like the outcome of that particular regexp (it looks a bit akward), but for the 99 other cases a regexp is much more cleaner and explicit. And this strpos-0-might-be-false-lets-use-===-akwardness only makes it worse.So for me the regexp is the simpler solution, but this is a matter of taste.. your opinion might differ.

reto 2009-11-10 10:22:06

Yeah, I see your point. I agree regexes are often cleaner, but sometimes they are harder to read - especially if you're not too experienced with them. Then again: you're right, strpos() isn't the most easy one to read, either ;)

Franz 2009-11-10 10:28:07

+1 for not answering the question by the book, but instead giving a better answer

Peter Lindqvist 2009-11-10 10:34:07

Answer 2

+3 A:

Don't know about php, but this should do it:

^[^.]*-[^.]*$

Kobi 2009-11-10 09:47:51

Don't forget the anchors! `^` and `$`

Tomalak 2009-11-10 09:48:56

@Tomalak - Thanks!

Kobi 2009-11-10 09:49:59

To make it more performant, use `^[^.-]*-[^.]*$`.

Gumbo 2009-11-10 10:00:49

@Gumbo: Sharp eyes, as always. ;-)

Tomalak 2009-11-10 10:10:18

Can you explain why it does make it more performant? I'm not that good with regexes... ;)

Franz 2009-11-10 10:14:09

@Franz: Since the `*` quantifier is greedy, the preceeding expression `[^.]` would consume as much as it can before backtracking will be used to match the rest of the expression. So if the test string is `foo-bar`, `[^.]*` will first match the whole string, then step back until `[^.]*-` matches `foo-` and then match the rest so that the whole expression matches. With `[^.-]*` the expression will always just match the `foo` without backtracking.

Gumbo 2009-11-10 10:17:10

Cool. Thanks, Gumbo.

Franz 2009-11-10 10:19:37

@Gumbo - thanks for that. The though did cross my mind, but I wasn't sure it's necessary. I'll read. Thanks!

Kobi 2009-11-10 10:33:37

Answer 3

+2 A:

no need regex for this, one method is to use strpos

strpos($mystr,"-" ) !== FALSE && strpos($mystr,"." ) === FALSE

ghostdog74 2009-11-10 09:50:39

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php regex for string containing a "." and "-"

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