Posted by Jake Gardner on 09/26/05 17:59

Murray: I could kick myself for not seeing that one (* = 0 or more,
well it sure found 0)

On 9/26/05, Murray @ PlanetThoughtful <lists@planetthoughtful.org> wrote:
> > I recently encountered a strange behaviour, could someone please
> > countercheck it, to either tell me there is an error in my pattern?
> >
> > I have a test string: "7005-N/52"
> > I have two match patterns: a) "/([0-9]*)\/(.*)/i"
> > b) "/([0-9]*)\-(.*)/i"
> > I check the test string with the help of preg_match, and they both
> > matched, but normally variant a) shouldn't have matched.
> >
> > Normally I test my patterns with the tool "The Regex Coach", and
> > according to this tool it shouldn't have matched.
> > PHP version is 5.0.4, PCRE extension version is 4.5 01-December-2003
>
> Hi Jens
>
> Your first pattern 'matches' because it finds a hit on the "/52" component
> of your test string.
>
> If you look at the pattern itself, it's because you're using the
> 'zero-or-more-occurrences' quantifier (ie "*") in the first part of your
> pattern: "([0-9]*)".
>
> It's a valid hit, because there are zero incidences of numeric characters
> immediately prior to the "/52" component of the test string.
>
> Changing the "*" to a "+" (at least one or more occurrences) could 'fix'
> that pattern (ie so that it doesn't match your string), depending on any
> other values being tested by it.
>
> Much warmth,
>
> Murray
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> http://www.planetthoughtful.org
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