您可以直接在函数中向内容添加过滤器。php并使用str\\u replace或一些preg\\u replace（regex）来更改内容的输出。未测试。尝试以下操作：

function add_class_to_img_and_p_in_content($content) {

   $pattern ="/<img(.*?)class=\\"(.*?)\\"(.*?)>/i";
   $replacement = \'<img$1class="$2 newclass newclasstwo"$3>\';

   $content = preg_replace($pattern, $replacement, $content);

   $pattern ="/<p(.*?)class=\\"(.*?)\\"(.*?)>/i";
   $replacement = \'<p$1class="$2 newclass newclasstwo"$3>\';

   $content = preg_replace($pattern, $replacement, $content);


   return $content;
}
add_filter(\'the_content\', \'add_class_to_img_and_p_in_content\',11);

function new_content($content) {

    $content = str_replace(\'<img\',\'<img class="newImgclass"\', $content);
    $content = str_replace(\'<p>\',\'<p class="newPclass">\', $content);

    return $content;
}

add_filter(\'the_content\',\'new_content\');