Re: [PHP-DEV] preg weirdness? From: Andrey Zmievski (zmievski <email protected>)
Date: 05/28/99

Rasmus Lerdorf wrote:
> Ok, just to test out the pcre stuff I did a couple of tests:
>
> $a="abc";
> echo preg_replace("/.*/","X",$a);
>
> Here are the results, replacing the regex argument each time:
>
> regex expected got
> /.*/ X XX <==
> /.+/ X X
> // <error> XaXbXcX <==
> /\w/ XXX XXX
> /^\w+$/ X X
> /\b/ XabcX XaXbXc <==
> /^\w*?/ Xabc Xabc
> /^\w+?/ Xbc Xbc
>
> The first one just looks wrong to me. But the behaviour is the same in
> ereg_replace, so I guess it is correct.
>
> I suppose the second surprising one can be explained. It is just sort of
> funny to think about though. There is exactly 1 nothing before and after
> every char in the string? Here preg_replace() differs from
> ereg_replace(). ereg_replace() will throw an error.
>
> And the third weird one looks like a bug to me. \b is supposed to be a
> word boundary. That is, it should match the transition from a \W to a \w
> and vice versa. I only see two word boundaries like that in the "abc"
> string. The actual output makes no sense unless the pcre library doesn't
> understand \b being a word boundary.

Ok, go ahead and test it now. I figured out a way to to fix this, but it
involved modifying the actual PCRE library a bit. But now, the tests you did
should work perfectly. I tested the same ones in Perl and they match with
what preg_replace does.

What this means though is that people won't be able to link against new
versions of PCRE unless we update the bundled one. It shouldn't be a big
deal to do it every time new PCRE comes out, but just in case, I emailed the
author and asked him to consider putting the changes I made into the PCRE.

-Andrey
* Anything will fit if you push hard enough * 

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