PHP - Regex find string within square brackets

I have the following sample text

Some HTML[caption id="attachment_146" align="alignleft" width="450" caption="Annette during 2008 WSOP"]<a href='123'><img src='xxx' /></a>[/caption]More HTML

I would like to use regex to identify if the above piece of string contains the caption part ... and if it does I need to extract its attributes and the content within the square brackets i.e. the a tag and img tag

So far I was able to come up with

preg_match('^\[caption(.*?)\]^', $content, $matches);

Which seems to be able to identify the opening caption 'tag'