Is there a library that ....

[eluser]cahva[/eluser]
There is an easy way to get GeSHi working right away.

First add autoloading(PHP5 feature) as described here. Basically you only need to add that __autoload function to your config.php.

Then download geshi from the site, and copy geshi.php and geshi folder to application/libraries. Rename geshi.php to GeSHi.php (thats the name of the class and autoload will find it also in *NIX systems which are case sensitive).

Then you're ready to go. Test it:

Code:

<?php
class Test extends Controller {

    function __construct()
    {
        parent::__construct();
    }
    
    function index()
    {
        $code = '
$foo = "foo";
echo "foo is {$foo}";

$testarray = array(
    "CI" => "rocks!",
    "PHP" => "rox!"
);

foreach ($testarray as $k=>$v)
{
    echo $k." ".$v."\n";
}
';
        $language = 'php';

        $geshi = new GeSHi($code, $language);

        echo $geshi->parse_code();
    }
}

For the bbcode, you can look into this basic function to parse bbcode tags:
http://www.php.net/manual/en/function.bb....php#93349

Create a helper of that function so you can use it anywhere you like.