Regex problem: finding part of string that *doesnt necessarily* have to be there

[Markus]

I was intruiged as to how to build a parse that would run like bbcode does.

So's i had a go at it, somewhat shakily and naively.

As was expected, i hit a snare: when searching for a [url=http...] i could easily turn this into a real url using
[php]
preg_replace('#\[url=(.*)\](.*)\[/url\]#', "<a href='$1'>$2</a>", $_string);
[/php]
The problem was hit when i wanted to give the user the option of an extra - the 'target' attribute. I managed to get it working using this:
[php]
preg_replace('#\[url=(.*) target=(.*)\](.*)\[/url\]#', "<a target='$2' href='$1'>$3</a>", $_string);
[/php]
but obviously if the target isn't present problems will arise.

So, my question is: how can i have extra(s*) in the url that dont have to be there?

And how would i go about adding others such as: title, name, id... etc.

Kind regards!

p.s. im terrible of thinking up thread titles! :(

[helimeef]

I was intruiged as to how to build a parse that would run like bbcode does.

So's i had a go at it, somewhat shakily and naively.

As was expected, i hit a snare: when searching for a [url=http...] i could easily turn this into a real url using
[php]
preg_replace('#\[url=(.*)\](.*)\[/url\]#', "<a href='$1'>$2</a>", $_string);
[/php]
The problem was hit when i wanted to give the user the option of an extra - the 'target' attribute. I managed to get it working using this:
[php]
preg_replace('#\[url=(.*) target=(.*)\](.*)\[/url\]#', "<a target='$2' href='$1'>$3</a>", $_string);
[/php]
but obviously if the target isn't present problems will arise.

So, my question is: how can i have extra(s*) in the url that dont have to be there?

And how would i go about adding others such as: title, name, id... etc.

Kind regards!

p.s. im terrible of thinking up thread titles! :(

It's simple, to make something optional, wrap it in parentheses and add a "?" at the end of it.
For example, let's say you wanted to search for "something is fantastic" but you want "is" to be optional:

/\bsomething( is)? fantastic\b/

The ? operator simple makes the last symbol optional, not the last word. A simple would be a set (something between parentheses) or a single character. So

is?

would match "i" or "is", but not "".

Hope that helped.
Visit http://regular-expressions.info to go through a complete walkthrough of Regexes.

[Markus]

It's simple, to make something optional, wrap it in parentheses and add a "?" at the end of it.
For example, let's say you wanted to search for "something is fantastic" but you want "is" to be optional:

/\bsomething( is)? fantastic\b/

The ? operator simple makes the last symbol optional, not the last word. A simple would be a set (something between parentheses) or a single character. So

is?

would match "i" or "is", but not "".

Hope that helped.
Visit http://regular-expressions.info to go through a complete walkthrough of Regexes.

Thanks alot helimeef, i'll have a go later - it's been a while since I posted this thread, so I'd kind of forgotten about it :P

Cheers