RegEx with optional part inside

Question

I'm pretty new to regular expression. Just tried to analyse a "BB-Code" that could do something like this:

Pattern:

\[element title=(.*)picture=(\d+)](.*)(?:\[caption](.*):?\[/caption])?\[/caption].*

Search:

[element title=element title picture=32]Lorem ipsum dolor[caption]Photo by John Doe[/caption][/element]

[element title=element title picture=32]Lorem ipsum dolor[/element]

Well, the caption-part should be optional and both entries should give results. How can I reach this?

Is the caption always at the end, immediately before `[/element]` ? — Aziz, Apr 30 '12 at 20:30
yes, the caption is always immediately before [/element] - if a caption is given. — wildhaber, Apr 30 '12 at 20:31
Check here how to parse BBCode: http://stackoverflow.com/questions/488963/best-way-to-parse-bbcode — anubhava, Apr 30 '12 at 20:35

Aziz · Accepted Answer · 2012-05-01T07:54:17.720

1

How about this:

\[element title=(.*)picture=(\d+)\](.*?)(\[caption\](.*)\[/caption\])?\[/element\]

It will match both:

[element title=element title picture=32]Lorem ipsum dolor[caption]Photo by John Doe[/caption][/element]

[element title=element title picture=32]Lorem ipsum dolor[/element]

Example

in PHP, you can use it this way:

$regex = '#\[element title=(.*)picture=(\d+)\](.*?)(\[caption\](.*)\[/caption\])?\[/element\]#i';
$text = '[element title=element title picture=32]Lorem ipsum dolor[caption]Photo by John Doe[/caption][/element]';    

preg_match ( $regex, $text, $match );

print_r( $match );

The array $match will have several elements. Those are the strings that are surrounded by round-brackets ( and ) in the regular expression. One of them is the caption text.

Program execution and output can be seen here http://ideone.com/vQ1T0.

edited May 01 '12 at 07:54

answered Apr 30 '12 at 20:36

Aziz

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you're right, both matches. but how to extract the "caption" in a group if available? – wildhaber Apr 30 '12 at 20:52
@snuffer.ch: what language are you using? PHP? – Aziz May 01 '12 at 04:50
Yes, I'm using PHP - Thanks a lot for your help :) – wildhaber May 01 '12 at 07:11

score 0 · Answer 2 · answered Apr 30 '12 at 20:36

0

\[element title=(.*) picture=[0-9]+\](.*)(\[caption\](.)*\[\caption\])?\[/element\]

answered Apr 30 '12 at 20:36

Ahmed Jolani

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RegEx with optional part inside

2 Answers2

Example