wpp_get_mostpopular Update

function wpp_get_mostpopular($args = NULL, $return = false) {

    if ( is_null( $args ) ) {
        echo do_shortcode('[wpp]');
    } else {
            if( is_array( $args ) ){
                $atts = '';
                foreach( $args as $key => $arg ){
                    $atts .= $key . '="' . $arg . '"';
                }
            } else {
                $atts = trim( str_replace( "&", " ", $args  ) );
            }

            $out = do_shortcode( '[wpp '.$atts.']' );

            if( $return )
                return $out;

            echo $out;
    }
}