是不是感觉有点晕晕啦，呵呵，如果对监听者设计模式熟悉的话，比较容易理解的。 打个比方说，教室有张三在看小说，李四在聊天。但是，他们都怕老师进入教师。 因此都监听老师来了的事件。只要老师来了，张三就停止看小说，李四也不能聊天。 有个同学就望风，发现老是来了。 他喊一声：某某老是来了。 然后，张三，李四动作就激发啦。 望风报信同学，是消息的发送者。

实现类似上面2个功能，wordpress主要2个常用函数是：

add_filter($tag, $function_to_add, $priority = 10, $accepted_args = 1) 添加消息主题$tag类型过滤器，过滤函数是：$function_to_add 该函数一定需要有返回值的；$priority是该函数执行优先级；数字越小将越先执行,accepted_args支持传入参数个数，默认是1。

apply_filters($tag, $value) ，发送过滤主题消息，$tag消息主题，$value 发送需要过滤内容。

PHP代码执行该过程原理

 

举例说明：

add_filter(‘the_title’,’filter_trim_title’,1,1);

实际实现类似：

$wp_filter[‘the_title’] []= array(‘function’=>’filter_trim_title’…) 用一个数组列表，记录消息所有映射函数，及所有传入参数

如果再有一条

add_filter(‘the_title’,’filter_substr_title’,1,1);

继续执行：

$wp_filter[‘the_title’] []= array(‘function’=>’filter_substr_title’…) ，该消息内容增加一条函数映射

如果这个时候，执行以下代码:apply_filters(‘the_title’,’testtest’)，代码执行将会是类似如下：

$args=’testtest’;

foreach(add_filter(‘the_title’) as $the)

{

$args = call_user_func_array($the['function'], array_slice($args, 1, (int) $the(‘accepted_args’])); ///循环将该消息所有函数，执行一次，将返回的值作为下一个函数传入值。这里foreach前 会按照优先级排序

}

return $args; ///返回过滤后结果

 

通过上面例子，会发现，添加消息过滤方法，跟发送消息可以不同地方，只要放到一个全局数组中就可以了。 你只要在开始时候，增加过滤消息映射配置，可以变得更多行。 然后，可以再任意地方，发出这类消息，并且传入输入字符。 你会发现，通过该功能做消息的过滤，将是很轻松事情。

我们经常下会有从数据库里面读出代码，然后想做输出，这个时候，我们需要做转义操作。如果你的系统在读出内容后，添加了过滤消息发送接口，你需要对输出数据进行处理很容易。如下举例子

在通用包含地方添加如下代码（functions.php是不错选择）

 

add_filters(‘the_content’,’filter_contents’);

function filter_contents($data) 

{

     return htmlspecialchars($data);

}

然后在读取数据库地方加入如下代码

function get_content($data)

{

      return apply_filters(‘the_content’,$data);  //这样将$data作为消息发送，内容数据一起发送出去，所有绑定了’the_content’消息的所有函数，按照顺序串起来过滤内容。第一个过滤后结果，作为第2个输入参数，直到最后一个处理完，返回了内容。就是apply_filters 获得的内容。

}

 

觉得不错吧，这种解耦方法。扩展性大大增强，在你的项目中也用下类似方法吧。 其实实现过程很容易的。 但是，带来的扩展性就非常巨大了。其它处理消息过滤器函数，还有：has_filter() current_filter() merge_filters() remove_filter() remove_all_filters() 等，感兴趣，可以去研究下 它们源码！

不早了，昨晚休息比较晚，今天这个时候，感觉很困了。 欢迎与我交流！

我看了，wordpress官方手册，里面没有对所有标签进行罗列。而如果你要进行wordpress插件开发，功能扩展开发。它的消息标签，是必须要有所了解的。 以下是我收集的所有filters类的消息标签，居然有500多个。

‘add_menu_classes’
‘admin_body_class’
‘admin_comment_types_dropdown’
‘admin_footer_text’
‘admin_memory_limit’
‘admin_post_thumbnail_html’
‘admin_title’
‘admin_url’
‘admired_attachment_size’
‘admired_author_bio_avatar_size’
‘admired_layout_classes’
‘admired_status_avatar’
‘admired_text’
‘akismet_comment_nonce’
‘akismet_delete_commentmeta_interval’
‘akismet_optimize_table’
‘akismet_show_user_comments_approved’
‘akismet_ua’
‘allowed_http_origin’
‘allowed_http_origins’
‘allowed_themes’
‘allow_subdirectory_install’
‘all_plugins’
‘all_themes’
‘attachment_fields_to_edit’
‘attachment_fields_to_save’
‘attachment_icon’
‘attachment_link’
‘attribute_escape’
‘auth_redirect_scheme’
‘autocomplete_users_for_site_admins’
‘blog_details’
‘blog_option_’
‘blog_redirect_404′
‘body_class’
‘browse-happy-notice’
‘bulk_actions-’
‘can_edit_network’
‘category_archive_meta’
‘category_description’
‘category_feed_link’
‘category_link’
‘close_comments_for_post_types’
‘comment_edit_pre’
‘comment_edit_redirect’
‘comment_form_default_fields’
‘comment_form_defaults’
‘comment_form_field_comment’
‘comment_form_logged_in’
‘comment_max_links_url’
‘comment_row_actions’
‘comments_array’
‘comments_open’
‘comments_per_page’
‘comments_popup_link_attributes’
‘comment_status_links’
‘comment_text’
‘contextual_help’
‘contextual_help_list’
‘core_version_check_locale’
‘cron_request’
‘cron_schedules’
‘customize_allowed_urls’
‘customize_value_’ . $this->id_data[ 'base'
'dashboard_incoming_links_feed'
'dashboard_incoming_links_link'
'dashboard_primary_feed'
'dashboard_primary_link'
'dashboard_primary_title'
'dashboard_secondary_feed'
'dashboard_secondary_link'
'dashboard_secondary_title'
'date_formats'
'dbdelta_create_queries'
'dbdelta_insert_queries'
'dbdelta_queries'
'default_content'
'default_contextual_help'
'default_excerpt'
'default_hidden_meta_boxes'
'default_option_'
'default_site_option_'
'default_title'
'delete_site_email_content'
'deprecated_argument_trigger_error'
'deprecated_file_trigger_error'
'deprecated_function_trigger_error'
'disable_captions'
'display_media_states'
'display_post_states'
'documentation_ignore_functions'
'doing_it_wrong_trigger_error'
'domain_exists'
'do_mu_upgrade'
'do_parse_request'
'dynamic_sidebar_params'
'editable_slug'
'edit_bookmark_link'
'edit_categories_per_page'
'edit_comment_link'
'editor_max_image_size'
'edit_post_link'
'edit_posts_per_page'
'edit_profile_url'
'edit_tag_link'
'edit_tags_per_page'
'edit_term_link'
'embed_56'
'embed_56com'
'embed_6cn'
'embed_cache_oembed_types'
'embed_defaults'
'embed_googlevideo'
'embed_handler_html'
'embed_ku6'
'embed_letv'
'embed_maybe_make_link'
'embed_oembed_html'
'embed_sina'
'embed_sohu'
'embed_tudou'
'embed_youku'
'embed_youtube'
'enable_edit_any_user_configuration'
'enable_post_by_email_configuration'
'enable_update_services_configuration'
'enter_title_here'
'esc_html'
'esc_textarea'
'exit_on_http_head'
'export_args'
'ext2type'
'extra_theme_headers'
'feed_content_type'
'force_filtered_html_on_import'
'format_to_edit'
'found_users_query'
'gallery_style'
'getarchives_join'
'get_archives_link'
'getarchives_where'
'get_attached_file'
'get_avatar_comment_types'
'get_bloginfo_rss'
'get_blogs_of_user'
'get_bookmarks'
'get_calendar'
'get_categories_taxonomy'
'get_comment_link'
'get_comment_text'
'get_delete_post_link'
'get_edit_bookmark_link'
'get_edit_comment_link'
'get_edit_post_link'
'get_edit_tag_link'
'get_edit_term_link'
'get_edit_user_link'
'getimagesize_mimes_to_exts'
'get_image_tag'
'get_lastpostdate'
'get_lastpostmodified'
'get_media_item_args'
'_get_page_link'
'get_pages'
'get_search_query'
'get_tags'
'get_terms_args'
'get_terms_fields'
'get_terms_orderby'
'gettext'
'gettext_with_context'
'get_the_author_'
'get_the_categories'
'get_the_excerpt'
'get_the_tags'
'get_the_terms'
'global_terms_enabled'
'graceful_fail'
'graceful_fail_template'
'hidden_meta_boxes'
'home_url'
'http_headers_useragent'
'http_origin'
'http_request_args'
'http_request_redirection_count'
'http_request_timeout'
'http_request_version'
'http_response'
'https_local_ssl_verify'
'icon_dir'
'icon_dirs'
'icon_dir_uri'
'image_add_caption_shortcode'
'image_downsize'
'image_editor_default_mime_type'
'image_make_intermediate_size'
'image_memory_limit'
'image_resize_dimensions'
'image_send_to_editor'
'image_send_to_editor_url'
'image_size_names_choose'
'import_upload_size_limit'
'install_plugins_nonmenu_tabs'
'install_plugins_tabs'
'install_themes_nonmenu_tabs'
'install_themes_tabs'
'intermediate_image_sizes'
'intermediate_image_sizes_advanced'
'is_email'
'is_email_address_unsafe'
'is_multi_author'
'is_protected_meta'
'jpeg_quality'
'js_escape'
'kses_allowed_protocols'
'lang_codes'
'list_cats'
'list_pages'
'load_default_embeds'
'load_image_to_edit_attachmenturl'
'load_image_to_edit_filesystempath'
'load_image_to_edit_path'
'load_textdomain_mofile'
'locale'
'login_form_bottom'
'login_form_defaults'
'login_form_middle'
'login_form_top'
'lostpassword_url'
'manage_media_columns'
'manage_pages_columns'
'manage_posts_columns'
'manage_' . $screen->id . '_columns'
'manage_sites_action_links'
'manage_taxonomies_for_attachment_columns'
'manage_users_custom_column'
'mce_css'
'mce_spellchecker_languages'
'media_meta'
'media_row_actions'
'media_send_to_editor'
'media_upload_mime_type_links'
'media_upload_tabs'
'media_view_settings'
'media_view_strings'
'mime_types'
'ms_user_row_actions'
'mu_dropdown_languages'
'mu_menu_items'
'myblogs_blog_actions'
'myblogs_options'
'nav_menu_attr_title'
'nav_menu_css_class'
'nav_menu_description'
'nav_menu_item_id'
'nav_menu_items_'
'nav_menu_meta_box_object'
'network_home_url'
'network_sites_updated_message_' . $_GET['updated']
‘network_site_url’
‘new_admin_email_content’
‘newblogname’
‘newblog_notify_siteadmin’
‘new_user_email_content’
‘newuser_notify_siteadmin’
‘next_comments_link_attributes’
‘next_posts_link_attributes’
‘ngettext’
‘ngettext_with_context’
‘nonce_life’
‘nonce_user_logged_out’
‘number_format_i18n’
‘oembed_dataparse’
‘oembed_fetch_url’
‘oembed_linktypes’
‘oembed_providers’
‘oembed_result’
‘option_’
‘option_enable_xmlrpc’
‘override_load_textdomain’
‘override_unload_textdomain’
‘page_attributes_dropdown_pages_args’
‘page_css_class’
‘page_link’
‘paginate_links’
‘pingback_ping_source_uri’
‘pingback_useragent’
‘pings_open’
‘plugin_install_action_links’
‘plugin_locale’
‘plugin_row_meta’
‘plupload_default_params’
‘plupload_default_settings’
‘plupload_init’
‘post_comments_feed_link_html’
‘post_date_column_time’
‘post_format_rewrite_base’
‘post_link_category’
‘postmeta_form_limit’
‘posts_request_ids’
‘post_thumbnail_html’
‘post_thumbnail_size’
‘post_type_archive_feed_link’
‘post_type_archive_link’
‘post_types_to_delete_with_user’
‘post_updated_messages’
‘pre_add_site_option_’
‘pre_comment_approved’
‘pre_ent2ncr’
‘pre_get_space_used’
‘pre_http_request’
‘pre_http_send_through_proxy’
‘pre_insert_term’
‘pre_option_’
‘pre_option_enable_xmlrpc’
‘pre_set_site_transient_’
‘pre_set_transient_’
‘pre_site_option_’
‘pre_site_transient_’
‘pre_transient_’
‘pre_update_option_’
‘pre_update_site_option_’
‘pre_upload_error’
‘pre_user_display_name’
‘preview_post_link’
‘previous_comments_link_attributes’
‘previous_posts_link_attributes’
‘print_scripts_array’
‘print_styles_array’
‘private_title_format’
‘protected_title_format’
‘pub_priv_sql_capability’
‘query’
‘quick_edit_dropdown_pages_args’
‘redirect_network_admin_request’
‘redirect_post_location’
‘redirect_user_admin_request’
‘request_filesystem_credentials’
‘role_has_cap’
‘rss_update_frequency’
‘rss_update_period’
‘safe_style_css’
‘salt’
‘sanitize_email’
‘sanitize_html_class’
‘sanitize_key’
‘sanitize_mime_type’
‘sanitize_trackback_urls’
‘sanitize_user’
‘screen_layout_columns’
‘screen_options_show_screen’
‘screen_settings’
‘script_loader_src’
‘search_link’
‘set_url_scheme’
‘show_admin_bar’
‘show_advanced_plugins’
‘show_network_site_users_add_existing_form’
‘show_network_site_users_add_new_form’
‘show_recent_comments_widget_style’
‘single_cat_title’
‘single_tag_title’
‘single_term_title’
‘site_option_’
‘site_transient_’
‘site_url’
‘smartadapt_attachment_size’
‘split_the_query’
‘status_header’
‘style_loader_src’
‘style_loader_tag’
‘stylesheet_directory’
‘stylesheet_directory_uri’
‘subdirectory_reserved_names’
‘tables_to_repair’
‘tag_archive_meta’
‘tag_cloud_sort’
‘tag_feed_link’
‘tag_link’
‘tag_row_actions’
‘tagsperpage’
‘taxonomy_feed_link’
‘teeny_mce_buttons’
‘teeny_mce_plugins’
‘template_directory’
‘template_directory_uri’
‘template_include’
‘term_name’
‘terms_clauses’
‘terms_to_edit’
‘the_author_posts_link’
‘the_category’
‘the_content_export’
‘the_content_more_link’
‘the_excerpt_export’
‘the_feed_link’
‘theme_action_links’
‘theme_install_actions’
‘theme_locale’
‘theme_root’
‘theme_root_uri’
‘theme_row_meta’
‘the_permalink’
‘the_search_query’
‘the_shortlink’
‘the_tags’
‘the_title’
‘the_title_rss’
‘thread_comments_depth_max’
‘time_formats’
‘transient_’
‘twentyeleven_attachment_size’
‘twentyeleven_author_bio_avatar_size’
‘twentyeleven_color_schemes’
‘twentyeleven_default_theme_options’
‘twentyeleven_header_image_height’
‘twentyeleven_header_image_width’
‘twentyeleven_layout_classes’
‘twentyeleven_layouts’
‘twentyeleven_status_avatar’
‘twentyeleven_theme_options_validate’
‘twentyten_attachment_height’
‘twentyten_attachment_size’
‘twentyten_author_bio_avatar_size’
‘twentyten_header_image_height’
‘twentyten_header_image_width’
‘twentytwelve_attachment_size’
‘twentytwelve_author_bio_avatar_size’
‘twentytwelve_status_avatar’
‘type_url_form_media’
‘update_attached_file’
‘update_feedback’
‘update_footer’
‘update_welcome_email’
‘update_welcome_subject’
‘update_welcome_user_email’
‘update_welcome_user_subject’
‘upload_dir’
‘upload_mimes’
‘upload_per_page’
‘upload_post_params’
‘upload_size_limit’
‘use_curl_transport’
‘use_default_gallery_style’
‘use_fsockopen_transport’
‘use_google_chrome_frame’
‘user_contactmethods’
‘user_dashboard_url’
‘user_has_cap’
‘user_row_actions’
‘use_streams_transport’
‘validate_current_theme’
‘validate_username’
‘views_’
‘walker_nav_menu_start_el’
‘whitelist_options’
‘widget_comments_args’
‘widget_posts_args’
‘widget_text’
‘widget_title’
‘wp_admin_bar_class’
‘wp_admin_css’
‘wp_admin_css_uri’
‘wp_cache_themes_persistently’
‘wp_checkdate’
‘wp_check_filetype_and_ext’
‘wp_check_post_lock_window’
‘wp_comment_reply’
‘wp_create_thumbnail’
‘wp_dashboard_widgets’
‘wp_default_editor’
‘wp_delete_file’
‘wp_die_ajax_handler’
‘wp_die_handler’
‘wp_die_xmlrpc_handler’
‘wp_dropdown_cats’
‘wp_edit_nav_menu_walker’
‘wp_editor_set_quality’
‘wp_feed_cache_transient_lifetime’
‘wp_fullscreen_buttons’
‘wp_generate_attachment_metadata’
‘wp_generate_tag_cloud’
‘wp_generator_type’
‘wp_get_attachment_image_attributes’
‘wp_get_attachment_link’
‘wp_get_attachment_metadata’
‘wp_get_attachment_thumb_file’
‘wp_get_attachment_thumb_url’
‘wp_get_attachment_url’
‘wp_get_nav_menu_items’
‘wp_get_nav_menus’
‘wp_get_update_data’
‘wp_handle_upload’
‘wp_handle_upload_prefilter’
‘wp_http_cookie_value’
‘wp_image_editors’
‘wp_insert_post_empty_content’
‘wp_insert_post_parent’
‘wp_is_large_network’
‘wp_kses_allowed_html’
‘wp_link_pages_args’
‘wp_list_bookmarks’
‘wp_list_categories’
‘wp_mail’
‘wp_mail_charset’
‘wp_mail_content_type’
‘wp_mail_from’
‘wp_mail_from_name’
‘wp_mime_type_icon’
‘wpmu_blogs_columns’
‘wpmu_delete_blog_upload_dir’
‘wpmu_drop_tables’
‘wpmu_signup_blog_notification_email’
‘wpmu_signup_blog_notification_subject’
‘wpmu_signup_user_notification_email’
‘wpmu_signup_user_notification_subject’
‘wpmu_users_columns’
‘wp_nav_menu’
‘wp_nav_menu_args’
‘wp_nav_menu_container_allowedtags’
‘wp_nav_menu_items’
‘wp_nav_menu_objects’
‘wp_network_dashboard_widgets’
‘wp_page_menu’
‘wp_page_menu_args’
‘wp_parse_str’
‘_wp_post_revision_fields’
‘wp_prepare_attachment_for_js’
‘wp_read_image_metadata’
‘wp_read_image_metadata_types’
‘_wp_relative_upload_path’
‘wp_setup_nav_menu_item’
‘wp_signup_location’
‘wp_sprintf’
‘wp_tag_cloud’
‘wp_terms_checklist_args’
‘wp_trim_words’
‘wp_unique_post_slug’
‘wp_unique_post_slug_is_bad_attachment_slug’
‘wp_unique_post_slug_is_bad_flat_slug’
‘wp_unique_post_slug_is_bad_hierarchical_slug’
‘wp_update_attachment_metadata’
‘wp_update_term_parent’
‘wp_upload_bits’
‘wp_user_dashboard_widgets’
‘wxr_export_skip_postmeta’
‘xmlrpc_blog_options’
‘xmlrpc_default_post_fields’
‘xmlrpc_default_posttype_fields’
‘xmlrpc_default_revision_fields’
‘xmlrpc_default_taxonomy_fields’
‘xmlrpc_default_user_fields’
‘xmlrpc_enabled’
‘xmlrpc_login_error’
‘xmlrpc_pingback_error’
‘xmlrpc_prepare_comment’
‘xmlrpc_prepare_media_item’
‘xmlrpc_prepare_page’
‘xmlrpc_prepare_post’
‘xmlrpc_prepare_post_type’
‘xmlrpc_prepare_taxonomy’
‘xmlrpc_prepare_term’
‘xmlrpc_prepare_user’
‘xmlrpc_wp_insert_post_data’

今天先做一个总列表，后面我会对一些filters 消息标签作用，用户做一些收集。 这类标签基本涵盖了wordpress 所有操作功能。 能够通过filter 消息标签，将所有功能发送数据进行一次过滤。然后再作用到目标，数据源可以来自前端，数据库，或者网络接口读取。也欢迎，朋友们一起来补充这些消息标签。