very hard regular expressions question?

Anon

ok... i wasted 8 hours on this... im a begginer in re but i think this ones very hard. i could not find an answer any where on the web so im posting here...

i have the following text.

hi =X=there! how are you?=xX= =X=This is the second sentence!=xX= =X=Third...=xX=

im trying to pick "=X=This is the second sentence!=xX=" USING "second" i used following re syntax but i failed..

/=X=.second.=xX=/

thanks in advance...

Anon

oops.. i used this

/=X=.second.=xX=/

this returns "=X=there! how are you?=xX= =X=This is the second sentence!=xX= =X=Third...=xX=" INSTEAD OF "=X=This is the second sentence!=xX="

badman

i think your problem is to break the string expression into parts whnever it encounters =X=. Once you break it ,you can choose which part you want to keep.is that right?

if yes, then you can use function explode(), this returns an array with strings expression stored in it. the expressions are seperated at the occurence of the pattern specified in the function.

Look for it in the php docs at www.php.net under string functions.

kparker

That's because the standard regular expressions are "greedy", i.e. they match the long possible pattern that matches the regex. If you use the perl-compatible module instead, you can ask it to be non-greedy. However, even if you do that, you may still have trouble with .* since it includes the starting pattern. That is, your current pattern, in text, asks to match:

'=X='
followed by zero or more characters of any type whatsoever
followed by 'second'
followed by zero or more characters of any type whatsoever
followed by '=xX='

Now, the non-greedy option with preg_match() will cause it match at the first '=xX=', so you won't get the "third" undesirable part, but I don't think it will cause the initial '=X=' to become un-anchored.

In short, splitting the string on '=xX=' (and then stripping off the leading =X= where present) will be a whole lot easier.