php preg_replace subpattern

I would like to highlight the last slug in url like this:

http://www.domain.org/school.html

Here's the pattern to capture the开发者_运维百科 slug:

$pattern = "/\/([^/]+)\.html$/";

How do I run preg_replace on url to replace the slug with <b>slug</b>?

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You need to preserve the / and filename suffix then for replacement:

= preg_replace("~(/)([^/]+)(\.html)$~", "$1<b>$2</b>$3", $urltext);

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Just simple as this - see examples on php site

preg_replace( $pattern, "<b>\$1</b>", $input );