kwatog

thanks, pdclark. I realized that after reviewing the codes. Anyhow, here’s my revised code

add_filter( 'the_content', 'after_more_ads', 10 );
function after_more_ads( $content ) {
    if ( is_single() ){
         $content = preg_replace("/<span id=\"more(.*?)span>/"," -- additional text here -- ",$content);
      }
    return $content;
}

somehow works.