[RESOLVED] Efficient highlighting

[cnperry]

So here's the situation: I'm working on an educational site that in which my boss would like to have certain keywords link to a glossary of terms + definitions. I understand the basics and could do it with some kind of loop on the terms from the database, and a preg_match/replace as the page renders...:
code=php
foreach($glossary_terms as $term)
{
$search="/({$term})/ie";
$link="<a href=\"glossary.php?term=$term\">$term</a>";
preg_replace($search,$link,$content)
}
[/code]

Besides running this script when new data is entered into the system, are there better (faster/more efficient) ways to do this? I've seen some sites that first render the page, then it appears a javascript (or something?) goes in and creates advert. links on major keywords . For example, notice how this page first renders w/o the double-underlined links, then as soon as its done links are inserted: http://howardforums.com/showthread.php?t=25116

Any ideas on how that's done (if indeed the way to do it)?

Thanks!
Cameron

[MarkR]

You can build a single regular expression which matches all of the words in the glossary. Use \b to mean "word boundary" (If I've remembered it correctly, go and look it up).

Then you can use a callback function to look up the definition and insert the appropriate html, therefore replacing your entire glossary with a single call to preg_replace_callback

Mark

[xblue]

This may even be possible without callbacks, I think.

Something along these lines

preg_replace('/\b'.implode('|', $glossary_terms).'\b/i', '<a href="glossary.php?term=$0">$0</a>', $content);

Just make sure your terms do not contain any characters that would be treated as special.

Using a backreference in the replacement argument also gets you around possible issues with losing capitalization of the link text, but then again might raise problems with capitalization in the link itself, so your glossary script would need to be prepared to process the terms no matter how they are capitalized.

[cnperry]

Thanks a millon, xblue and MarkR! That seems to be the trick! I suppose I just didn't fully understand the preg_replace function very well.

Everything seems to be working as advertised...

Take care,
Cameron