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Posted by Jasen Betts on 02/10/06 22:21
On 2006-02-09, Jim Michaels <jmichae3@nospam.yahoo.com> wrote:
>
> "Steve" <ThisOne@Aint.Valid> wrote in message
> news:pan.2006.01.19.07.57.27.732286@Aint.Valid...
>> On Wed, 18 Jan 2006 21:36:20 -0800, yawnmoth wrote:
>>
>>> Say I have the following script:
>>>
>>> <?
>>> $string = 'test';
>>> if (eregi("^[a-z0-9| |\,\-\+\.]+$",$string))
>>> {
>>> echo 'matches!';
>>> }
>>> else
>>> {
>>> echo 'no match';
>>> }
>>> ?>
>>>
>>> Why does $string = 'te\st' yield a match? The ereg expression doesn't
>>> have a \\ in it...
>> the \ is escaping the s, so is invisible to the regular expression. To
>> have an \ in the string, you'd need to see \\
>>
>>>
>>> Also, what does | | do? Normally, it'd mean 'or', but inside of []'s?
>>> And two of them?
>> Well, one | inside a class ( [...] ) matches |. Not too sure what 2 of
>> them mean, though. The space between them will also be matched. Using | as
>> an or would require the use of parentheses as well.
>>
>> tbh, I'm not too sure the author really knew what they were doing, as
>> almost all those characters with special powers ( like \ ) lose them all
>> when between []'s (:
>
>
><?php print preg_match('/[\s]/'," \t "); ?>
> 1
> Where did you hear this? this has been a part of Perl RE's for a long time.
> Perl's REs were pretty much ported to PHP. PERL RE was POSIX if I am not
> mistaken.
Possibly they share a common ancestor. They are different now.
> I've been able to escape things in [] character classes in UNIX and
> grep-like programs for as long as I can remember. I thought I remember
> having to so I could avoid weird behavior.
I suspect you're mistaken.
this from regex(7):
..
.. To include a literal ]' in the list, make it the first character (fol-
.. lowing a possible ^'). To include a literal -', make it the first or
.. last character, or the second endpoint of a range. To use a literal
.. '-' as the first endpoint of a range, enclose it in [.' and .]' to
.. make it a collating element (see below). With the exception of these
.. and some combinations using [' (see next paragraphs), all other spe-
.. cial characters, including \', lose their special significance within
.. a bracket expression.
> it's probably not safe to avoid escaping "-" because of its interpretation
> as a range. better to be safe than sorry.
depends on the definition of safe.
Bye.
Jasen
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