RegEx Replace?

[Alan M Dunsmuir]

I am confused by the operation of the RegEx Replace functions provided
by PHP.

I understand, of course, what is intended if the 'Replace' string is a
simple character string, to be slotted into the target whenever a match
is achieved.

But what is intended when the 'Replace' string is itself a RegEx string?

How does that work?

[Franz Marksteiner]

Re: RegEx Replace?

Alan M Dunsmuir wrote:

I am confused by the operation of the RegEx Replace functions provided
by PHP.
>
I understand, of course, what is intended if the 'Replace' string is a
simple character string, to be slotted into the target whenever a
match is achieved.
>
But what is intended when the 'Replace' string is itself a RegEx
string?
How does that work?

That is a little tricky indeed:
You can address matching subpatterns from your RegExp in the replacement
string.
Thatfore you have to embrace those subpatterns within "()", which you can
now use with $1, $2, ... in the replacement.

--
Freundliche Grüße,
Franz Marksteiner

[Rik Wasmus]

Re: RegEx Replace?

On Mon, 04 Feb 2008 14:48:37 +0100, Alan M Dunsmuir
<alan@moonrake. demon.co.ukwrot e:

I am confused by the operation of the RegEx Replace functions provided
by PHP.
>
I understand, of course, what is intended if the 'Replace' string is a
simple character string, to be slotted into the target whenever a match
is achieved.
>
But what is intended when the 'Replace' string is itself a RegEx string?

What do you mean with 'the replace string is a regex string'? Could you
give an example for this? If you're replacment string could be interpreted
as a regex this won't do a thing, it will be 'just another string' as far
as PHP is concerned.

If you want to do further processing on a matched string, you could use
the subpatterns with $1, $2 etc. (be sure to use _single_ quotes around
the string). If the operation is more complex, you can use either the /e
modifier or preg_replace_ca llback() to use a (custom) function to perform
more operations on a string.
--
Rik Wasmus

[Alan M Dunsmuir]

Re: RegEx Replace?

Franz Marksteiner wrote:

>
That is a little tricky indeed:
You can address matching subpatterns from your RegExp in the replacement
string.
Thatfore you have to embrace those subpatterns within "()", which you
can now use with $1, $2, ... in the replacement.
>

I clearly don't have the hang of it yet.

I tried (using Forta's RegEx Tester) with the RegEx ([0-9]{3})[0-9]{2}
and the replacement string ($1), offering it the text 1asc1234wer9876 5
and expecting to see 987.

In fact I got 1asc1234wer(987 ) and realised that non-matches must
survive unchanged.

But where did the ( and ) come from?

[Alan M Dunsmuir]

Re: RegEx Replace?

Rik Wasmus wrote:

I expect you did this:
>
preg_replace('/([0-9]{3})[0-9]{2}/','($1)','1asc1 234wer98765');
(if not, don't make use guess, _give the code_)

I didn't use code directly. I used the Forta RegEx Tester
(http://www.forta.com/books/0672325667/), which is a downloadable applet
with available flavours .NET, PHP, JavaScript, etc.

For convenient I used the JavaScript version on Firefox.

[Franz Marksteiner]

Re: RegEx Replace?

Alan M Dunsmuir wrote:

Rik Wasmus wrote:

>I expect you did this:
>>
>preg_replace ('/([0-9]{3})[0-9]{2}/','($1)','1asc1 234wer98765');
>(if not, don't make use guess, _give the code_)

>
I didn't use code directly. I used the Forta RegEx Tester
(http://www.forta.com/books/0672325667/), which is a downloadable
applet with available flavours .NET, PHP, JavaScript, etc.
>
For convenient I used the JavaScript version on Firefox.

Don`t worry, just leave out the "()" in the replacement string.

--
Freundliche Grüße,
Franz Marksteiner