苦苦挣扎的PHP正则表达式

Question

I'm struggling with what I imagine is quite a simple regex for a preg_match_all() call. I'm looking to mimic the Wikimedia style internal links system which will turn something like this [[link]] into a link.

I'm looking for a regex that will search a string for any example of [[foobar]] and return "foobar" to me. foobar should really be wild.

I've tried the following:

<?php
 $content = "Lorem ipsum dolor [[sit]] amet, consectetur adipiscing [[elit]].";
 $links = preg_match_all("[[*]]",$content,$matches);
 print_r($matches);
?>

I'm not getting much of anything. Any help would be appreciated.

Answer 1

You need to escape [ as \[ and then match the overall expression with the un-greedy flag U.

$content = "Lorem ipsum dolor [[sit]] amet, consectetur adipiscing [[elit]].";
$links = preg_match_all("/\[\[(.*)]]/U",$content,$matches);
print_r($matches);

Array(
    [0] => Array (
        [0] => [[sit]]
        [1] => [[elit]]
    )
    [1] => Array (
        [0] => sit
        [1] => elit
    )
)

EDIT: user ridgerunner pointed out that it's considered bad practice to use the /U modifier because it turns all matching quantifiers greedy, including ungreedy ones. The suggested matching code is (.*?) instead of what's posted above, and it produces the same equivalent answer.

$links = preg_match_all("/\[\[(.*?)]]/",$content,$matches);