markdown 有用的WordPress插件片段
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# Integratig your plugin into WordPress
## Menus and submenus
`add_menu_page( $page_title, $menu_title, $capability, $menu_slug, $function, $icon_url, $position );`
- `$page_title`: displayed between `<title>` tags
- `$menu_title`: displayed on the dashboard
- `$capability`: minimum capability required to access the menu
- `$function`: function called to display page content
- `$icon_url`: URL to custom image to use as menu icon
- `$position`: order in the menu
Use `admin_menu` action hook to trigger menu code.
*Example:*
```php
add_action( 'admin_menu', 'lzp_create_menu' );
function lzp_create_menu() {
// create custom menu
add_menu_page(
'My Plugin Settings Page',
'My Plugin Settings',
'manage_options', // only administrators can access
__FILE__,
'lzp_settings_page',
plugins_url('/images/wp-icon.png', __FILE__)
);
}
```
Do not forget to add where the settings can be accessed in your documentation.
### Submenus
`add_submenu_page( $parent_slug, $page_title, $menu_title, $capability, $menu_slug, $function );`
- `$parent_slug`: previously defined `$menu_slug` of the the top-level menu
- `$page_title`: displayed between `<title>` tags
- `$menu_title`: displayed on the dashboard
- `$capability`: minimum capability required to access the menu
- `$function`: function called to display page content
*Example:*
```php
add_action( 'admin_menu', 'lzp_create_menu' );
function lzp_create_menu() {
// create custom menu
add_menu_page(
'My Plugin Settings Page',
'My Plugin Settings',
'manage_options', // only administrators can access
__FILE__,
'lzp_settings_page',
plugins_url('/images/wp-icon.png', __FILE__)
);
// create custom sub menus
add_submenu_page( __FILE__, 'About My Plugin', 'About', 'manage_options', __FILE__ . 'about', 'lzp_about_page' );
add_submenu_page( __FILE__, 'My Plugin Help', 'Help', 'manage_options', __FILE__ . 'help', 'lzp_help_page' );
add_submenu_page( __FILE__, 'Uninstall My Plugin', 'Uninstall', 'manage_options', __FILE__ . 'uninstall', 'lzp_uninstall_page' );
}
```
Do not forget to add where the settings can be accessed in your documentation.
### Add a menu ton an existing menu
`add_options_page( $page_title, $menu_title, $capability, $menu_slug, $function );`
- `$page_title`: displayed between `<title>` tags
- `$menu_title`: displayed on the dashboard
- `$capability`: minimum capability required to access the menu
- `$function`: function called to display page content
*Example:*
```php
add_action( 'admin_menu', 'lzp_create_menu' );
function lzp_create_menu() {
// create submenu under Settings
add_options_page(
'My Plugin Settings Page',
'My Plugin Settings',
'manage_options', // only administrators can access
__FILE__,
'lzp_settings_page'
);
}
```
Do not forget to add where the settings can be accessed in your documentation.
List of all WordPress submenu functions
- `add_dashboard_page`
- `add_posts_page`
- `add_media_page`
- `add_links_page`
- `add_pages_page`
- `add_comments_page`
- `add_theme_page`
- `add_plugins_page`
- `add_users_page`
- `add_management_page`
- `add_options_page`
If your plugin only needs a single options page, add it to an existing menu. Otherwise, it's better to create a new top-level menu.
## Widgets
### The `WP_Widget` class
- Extend the `WP_Widget` class
```php
class lzp_mywidget extends WP_Widget {
function lzp_mywidget() {
// processes the widget
}
function form( $instance ) {
// displays widget form in the admin dashboard
}
function update( $new_instance, $old_instance ) {
// processes widget options to save
}
function widget( $args, $instance ) {
// displays the widget
}
}
```
- Create a widget
```php
add_action( 'widgets_init', 'lzp_mywidget_register_widgets' );
function lzp_mywidget_register_widgets() {
register_widgets( 'lzp_mywidget' );
}
```
*Example: Widget to display favorite Movie and Song*
```php
class lzp_movie_and_song extends WP_Widget {
function lzp_movie_and_song() {
$widget_ops = [
'classname' => 'lzp_mywidget_widget_class', // class added to the li element of widget
'description' => 'Display a user\'s favorite movie and song', // description showed on widget screen
];
$this->WP_Widget( 'lzp_movie_and_song', 'Movie and Song', $widget_ops );
}
function form( $instance ) {
$defaults = [
'title' => 'Movie and Song',
'movie' => '',
'song' => '',
];
$title = $instance['title'];
$movie = $instance['movie'];
$song = $instance['song'];
?>
<p>Title:
}
function update( $new_instance, $old_instance ) {
// processes widget options to save
}
function widget( $args, $instance ) {
// displays the widget
}
}# Actions and Filters
- Actions: execute a function at a certain point
- Filters: manipulate the output passed through the hook
## Actions
### Create and Remove actions
- Create custom action hook
- `$tag`: name of the action hook to create
- `$args`: needed args (optionnal)
```php
do_action( $tag, $arg1, $arg2, ...);
```
- Add an function to an action hook
- `$tag`: name of the action hook
- `$function`: name of called function
- `$priority`: lower number, higher priority order
- `$accepted_args`: parameters passed to the $function
```php
add_action( $tag, $function, $priority, $accepted_args );
```
- Action hook in a class :
```php
add_action( $tag, array( &$this, $method_to_add ) );
```
- Remove a function to an action hook
```php
remove_action( $tag, $function, $priority, $accepted_args );
```
To remove default WordPress actions, have a look at `wp-includes/default-filters.php`.
- Remove all actions of a particular tag (**Not advised**)
```php
remove_all_actions( $tag, $priority );
```
### Test actions
- Check if hook has actions
```php
has_action( $tag, (opt) $function )
```
Returns true, false or priority
- Check if action hook has already been executed and number of executions if so:
```php
did_action( $tag )
```
*Example:*
```php
if ( did_action( 'plugin_loaded' ) ) {
define( 'LZP_READY', true );
}
```
### Commonly used action hooks
- `plugins_loaded`
A WordPress plugin should do its setup on this hook.
*Example:*
```php
add_action( 'plugins-loaded', 'lzp_setup' );
function lzp_setup() {
add_action( ... );
}
```
**Creating a setup function and hook it to `plugins_loaded` is always a good idea**
- `init`
Nearly everything is ready after this hook => To use when you need all the information from WordPress to be available.
*Example:*
```php
add_action( 'init', 'lzp_add_excerpts_to_pages' );
```
- `admin_menu`
Called when an admin page loads.
- `template_redirect`
The point where WordPress knows which page a user is viewing. Executed just before the theme template is chosen for the view.
A good hook when in need of loading code only for specific page view (loading a specific stylesheet....).
- `wp_head`
Launched by `wp_head()` function on front end
Good hook when in need of adding `HTML` between `<head>` tags
**Do not add Javascript or CSS - except for specific cases - with this hook !**
- `widgets_init`
Execute custom widgets
## Filters
### Create and remove filters
- Create custom filter hook
```php
apply_filters( $tag, $value );
```
- Add function to a filter hook
```php
add_filter( $tag, $function, $priority, $accepted_args );
```
- And in a class :
```php
add_filter( $tag, array( &$this, $method_to_add ) );
```
- Remove function from filter hook
```php
remove_filter( $tag, $function, $priority, $accepted_args );
```
- Remove all functions from a filter hook
```php
remove_all_filters( $tag, $priority );
```
### Test Filters
```php
has_filter( $tag, $function );
```
### Commonly used filter hooks
- `the_content`
Passes a post's content to any filters registered to `the_content`.
*Example :*
```php
add_filter( 'the_content', 'lzp_add_related_posts_to_content' );
function lzp_add_related_posts_to_content( $content ) {
// If not viewing a singular post, just return
if ( ! is_singular( 'post' ) ) {
return $content;
}
// Get the categories of current post
$terms = get_the_terms( get_the_ID(), 'category' );
// Loop through the categories and put their IDs in an array
$categories = [];
foreach ( $terms as $term ) {
$categories[] = $term->term_id;
}
// Query posts with the same category
$loop = new WP_Query ([
'cat__in' => $categories,
'posts_per_page' => 5,
'post__not_in' => [get_the_ID()],
'orderby' => 'rand'
]);
// Loop through Related posts, if any
if ( $loop->have_posts() ) {
// Open related posts list
$content .= '<ul class="related-posts">';
while ( $loop->have_posts() ) {
$loop->the_post();
// Add related post to the list and format it
$content .= the_title(
'<li><a href="' . get_permalink() . '">',
'</a></li>',
false
);
}
// Close related posts list
$content .= '</ul>';
// Reset Query
wp_reset_query();
}
return $content;
}
```
- `the_title`
- `comment_text`
- `template_include`
- `front_page_template`
- `home_template`
- `single_template`
- `page_template`
- `attachment_template`
- `archive_template`
- `category_template`
- `tag_template`
- `author_template`
- `date_template`
- `archive_template`
- `search_template`
- `404_template`
- `index_template`
## Common functions
### Current hook
- Return the name of the current hook (action or filter)
```php
current_filter();
```
### Quick return
```php
__return_false();
```
```php
__return_true();
```
```php
__return_empty_array();
```
```php
__return_zero();
```# Create a new plugin
## Header
```php
<?php
/*
Plugin Name: My Plugin
Plugin URI: https://loren.zone/wordpress-plugins/my-plugin
Description: A brief description of what the plugin does
Version: 1.0
Author: Lorenzo Milesi
Author URI: https://loren.zone
License: GPL
*/
/* Copyright YEAR PLUGIN_AUTHOR_NAME (email : PLUGIN AUTHOR EMAIL)
This program is free software; you can redistribute it and/or modify
it under the terms of the GNU General Public License as published by
the Free Software Foundation; either version 2 of the License, or
(at your option) any later version.
This program is distributed in the hope that it will be useful,
but WITHOUT ANY WARRANTY; without even the implied warranty of
MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
GNU General Public License for more details.
You should have received a copy of the GNU General Public License
along with this program; if not, write to the Free Software
Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
*/
```
## Path Functions
### Local paths
- Local Path to Plugin folder
```php
echo plugin_dir_path(__FILE__);
```
- Local path to subfolder
```php
echo plugin_dir_path(__FILE__).'js/scripts.js';
```
### URL paths
- Full plugins directory URL (best friend function)
- `$path` - (string) (optional) — Path relative to the plugins URL
- `$plugin` -(string) (optional) — Plugin file that you want to be relative (that is, pass in __FILE__)
```php
plugins_url( $path, $plugin );
```
*Example:*
```php
echo '<img src="' . plugins_url( 'images/icon.png', __FILE__ ) . '">';
```
returns
```html
<img src="http://example.com/wp-content/plugins/my-custom-plugin/images/icon.png">
```
- supports mu-plugins
- auto detects ssl
- uses WP_PLUGIN_URL and WPMU_PLUGIN_URL
- Full includes directory URL
*https://website.com/wp-includes*
`includes_url();`
- Full content directory URL
*https://website.com/wp-content*
`content_url();`
- Full admin directory URL
*https://website.com/wp-admin*
`admin_url();`
- home and site URL
**/!\ differences are made within wp_options table**
`home_url(); // URL to visit website`
`site_url(); // URL to WordPress core files`
## Activation hooks
- Plugin activation function: triggered when plugin gets activated
- `$file` - (string) (required) — Path to the primary plugin file
- `$function` - (string) (required) — The function to be executed when the plugin is activated
*Example:*
```php
register_activation_hook(__FILE__,'lzp_install');
```
- Plugin deactivation function: triggered when plugin gets deactivated
- `$file` - (string) (required) — Path to the primary plugin file
- `$function` - (string) (required) — The function to be executed when the plugin is deactivated
*Example:*
```php
register_deactivation_hook(__FILE__,'lzp_deactivate');
```
**/!\ DO NOT include uninstall functionnality here (since WP auto update deactivates all plugins)**
## Uninstall
- Method 1 (cleanest) user `uninstall.php` file
```php
if(!defided('WP_UNISTALL_PLUGIN'))
exit();
// Delete option from options table
delete_option('lzp_options');
// Remove any additionnal options and custom tables
```
- Method 2 (not advised) `register_uninstall_hook($file, $function);`
**/!\ must be INSIDE activation hook**
```php
register_activation_hook( __FILE__, 'lzp_activate' );
function lzp_activate() {
//register the uninstall function
register_uninstall_hook( __FILE__, 'lzp_uninstaller' );
}
function lzp_uninstaller() {
//delete any options, tables, etc the plugin created
delete_option( 'lzp_options' );
}
```
# Some useful WordPress Links
## WordPress Coding Standards
https://codex.wordpress.org/WordPress_Coding_Standards以上是关于markdown 有用的WordPress插件片段的主要内容，如果未能解决你的问题，请参考以下文章
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