tech-geeks

class MakeItLink {
    protected function _link_www( $matches ) {
        $url = $matches[2];
        $url = MakeItLink::cleanURL( $url );
        if( empty( $url ) ) {
            return $matches[0];
        }
 
        return "{$matches[1]}{$url}";
    }
 
    public function cleanURL( $url ) {
        if( $url == '' ) {
            return $url;
        }
 
        $url = preg_replace( "|[^a-z0-9-~+_.?#=!&;,/:%@$*'()x80-xff]|i", '', $url );
        $url = str_replace( array( "%0d", "%0a" ), '', $url );
        $url = str_replace( ";//", "://", $url );
 
        /* If the URL doesn't appear to contain a scheme, we
         * presume it needs http:// appended (unless a relative
         * link starting with / or a php file).
         */
        if(
            strpos( $url, ":" ) === false
            && substr( $url, 0, 1 ) != "/"
            && !preg_match( "|^[a-z0-9-]+?.php|i", $url )
        ) {
            $url = "http://{$url}";
        }
 
        // Replace ampersans and single quotes
        $url = preg_replace( "|&([^#])(?![a-z]{2,8};)|", "&$1", $url );
        $url = str_replace( "'", "'", $url );
 
        return $url;
    }
 
    public function transform( $text ) {
        $text = " {$text}";
 
        $text = preg_replace_callback(
            '#(?])(\()?([\w]+?://(?:[\w\\x80-\\xff\#$%&~/\-=?@\[\](+]|[.,;:](?![\s<])|(?(1)\)(?![\s<])|\)))*)#is',
            array( 'MakeItLink', '_link_www' ),
            $text
        );
 
        $text = preg_replace( '#(]+?>|>))]+?>([^>]+?)#i', "$1$3", $text )

Live Demo of Google Apps management of Chrome OS starts around 22:30 into the presentation