Plugin Frase del día: action, filter y widget

<?php
/*
 Plugin Name: Frase del día
 Plugin URI: https://es.wikiquote.org/wiki/Portada
 Description: Muestra una frase del día diferente
 Author: Jota Peich
 Version: 1.0
 Author URI: http://intelisen.com
 */

function frase_getFrase() {
 $upload = wp_upload_dir();

 $frases = file($upload['basedir'] . "/frases.txt");
 return $frases[rand(0, count($frases) - 1)];
}

function frase_ponFrase() {
 echo frase_getFrase();
}

add_action('admin_notices', 'frase_ponFrase');

function frase_filtro($contenido) {
 return $contenido . "<br/>" . frase_getFrase();
}

add_filter("the_content", 'frase_filtro');

class FraseWidget extends WP_Widget {

 function FraseWidget() {
 $widget_ops = array('classname' => 'FraseWidget', 'description' => 'Muestra una frase del día');
 $this->WP_Widget('FraseWidget', 'Frase del día', $widget_ops);
 }

 function form($instance) {
 $instance = wp_parse_args((array) $instance, array('title' => ''));
 $title = $instance['title'];
 ?>
 <p><label for="<?php echo $this->get_field_id('title'); ?>"><?= _e('Title') ?>: <input class="widefat" id="<?php echo $this->get_field_id('title'); ?>" name="<?php echo $this->get_field_name('title'); ?>" type="text" value="<?php echo attribute_escape($title); ?>" /></label></p>
 <?php
 }

 function update($new_instance, $old_instance) {
 $instance = $old_instance;
 $instance['title'] = $new_instance['title'];
 return $instance;
 }

 function widget($args, $instance) {
 extract($args, EXTR_SKIP);

 echo $before_widget;
 $title = empty($instance['title']) ? ' ' : apply_filters('widget_title', $instance['title']);

 if (!empty($title))
 echo $before_title . $title . $after_title;;

 echo frase_getFrase();

 echo $after_widget;
 }

}

add_action('widgets_init', create_function('', 'return register_widget("FraseWidget");'));