如何在 WordPress 插件中包含 CSS 和 jQuery？

See http://codex.wordpress.org/Function_Reference/wp_enqueue_script

Example

<?php
function my_init_method() {
wp_deregister_script( 'jquery' );
wp_register_script( 'jquery', 'http://ajax.googleapis.com/ajax/libs/jquery/1.4/jquery.min.js');
}


add_action('init', 'my_init_method');
?>

For styles wp_register_style( 'namespace', 'http://locationofcss.com/mycss.css' );

Then use: wp_enqueue_style('namespace'); wherever you want the css to load.

Scripts are as above but the quicker way for loading jquery is just to use enqueue loaded in an init for the page you want it to load on: wp_enqueue_script('jquery');

Unless of course you want to use the google repository for jquery.

You can also conditionally load the jquery library that your script is dependent on:

wp_enqueue_script('namespaceformyscript', 'http://locationofscript.com/myscript.js', array('jquery'));

Update Sept. 2017

I wrote this answer a while ago. I should clarify that the best place to enqueue your scripts and styles is within the wp_enqueue_scripts hook. So for example:

add_action('wp_enqueue_scripts', 'callback_for_setting_up_scripts');
function callback_for_setting_up_scripts() {
wp_register_style( 'namespace', 'http://locationofcss.com/mycss.css' );
wp_enqueue_style( 'namespace' );
wp_enqueue_script( 'namespaceformyscript', 'http://locationofscript.com/myscript.js', array( 'jquery' ) );
}

The wp_enqueue_scripts action will set things up for the "frontend". You can use the admin_enqueue_scripts action for the backend (anywhere within wp-admin) and the login_enqueue_scripts action for the login page.

Put it in the init() function for your plugin.

function your_namespace() {
wp_register_style('your_namespace', plugins_url('style.css',__FILE__ ));
wp_enqueue_style('your_namespace');
wp_register_script( 'your_namespace', plugins_url('your_script.js',__FILE__ ));
wp_enqueue_script('your_namespace');
}


add_action( 'admin_init','your_namespace');

It took me also some time before I found the (for me) best solution which is foolproof imho.

Cheers

To include CSS and jQuery in your plugin is easy, try this:

// register jquery and style on initialization
add_action('init', 'register_script');
function register_script() {
wp_register_script( 'custom_jquery', plugins_url('/js/custom-jquery.js', __FILE__), array('jquery'), '2.5.1' );


wp_register_style( 'new_style', plugins_url('/css/new-style.css', __FILE__), false, '1.0.0', 'all');
}


// use the registered jquery and style above
add_action('wp_enqueue_scripts', 'enqueue_style');


function enqueue_style(){
wp_enqueue_script('custom_jquery');


wp_enqueue_style( 'new_style' );
}

I found this great snipped from this site How to include jQuery and CSS in WordPress – The WordPress Way

Hope that helps.

Accepted answer is incomplete. You should use the right hook: wp_enqueue_scripts

Example:

    function add_my_css_and_my_js_files(){
wp_enqueue_script('your-script-name', $this->urlpath  . '/your-script-filename.js', array('jquery'), '1.2.3', true);
wp_enqueue_style( 'your-stylesheet-name', plugins_url('/css/new-style.css', __FILE__), false, '1.0.0', 'all');
}
add_action('wp_enqueue_scripts', "add_my_css_and_my_js_files");

Just to append to @pixeline's answer (tried to add a simple comment but the site said I needed 50 reputation).

If you are writing your plugin for the admin section then you should use:

add_action('admin_enqueue_scripts', "add_my_css_and_my_js_files");

The admin_enqueueu_scripts is the correct hook for the admin section, use wp_enqueue_scripts for the front end.

First you need to register the style and css using wp_register_script() and wp_register_style() functions

 //registering javascript and css
wp_register_script ( 'mysample', plugins_url ( 'js/myjs.js', __FILE__ ) );
wp_register_style ( 'mysample', plugins_url ( 'css/mystyle.css', __FILE__ ) );

After this you can call the wp_enqueue_script() and wp_enqueue_style() functions for loading the js and css in required page

wp_enqueue_script('mysample');
wp_enqueue_style('mysample');

I fount a nice example here http://wiki.workassis.com/wordpress-create-advanced-custom-plugin-using-oop/

You can use the following function to enqueue script or style from plugin.

function my_enqueued_assets() {
wp_enqueue_script('my-js-file', plugin_dir_url(__FILE__) . '/js/script.js', '', time());
wp_enqueue_style('my-css-file', plugin_dir_url(__FILE__) . '/css/style.css', '', time());
}
add_action('wp_enqueue_scripts', 'my_enqueued_assets');

Very Simple:

Adding JS/CSS in the Front End:

function enqueue_related_pages_scripts_and_styles(){
wp_enqueue_style('related-styles', plugins_url('/css/bootstrap.min.css', __FILE__));
wp_enqueue_script('releated-script', plugins_url( '/js/custom.js' , __FILE__ ), array('jquery','jquery-ui-droppable','jquery-ui-draggable', 'jquery-ui-sortable'));
}
add_action('wp_enqueue_scripts','enqueue_related_pages_scripts_and_styles');

Adding JS/CSS in WP Admin Area:

function enqueue_related_pages_scripts_and_styles(){
wp_enqueue_style('related-pages-admin-styles',  get_stylesheet_directory_uri() . '/admin-related-pages-styles.css');
wp_enqueue_script('releated-pages-admin-script', plugins_url( '/js/custom.js' , __FILE__ ), array('jquery','jquery-ui-droppable','jquery-ui-draggable', 'jquery-ui-sortable'));
}
add_action('admin_enqueue_scripts','enqueue_related_pages_scripts_and_styles');

You can add scripts and css in back end and front end with this following code: This is simple class and the functions are called in object oriented way.

class AtiBlogTest {
function register(){
//for backend
add_action( 'admin_enqueue_scripts', array($this,'backendEnqueue'));
//for frontend
add_action( 'wp_enqueue_scripts', array($this,'frontendEnqueue'));
}
function backendEnqueue(){
wp_enqueue_style( 'AtiBlogTestStyle', plugins_url( '/assets/css/admin_mystyle.css', __FILE__ ));
wp_enqueue_script( 'AtiBlogTestScript', plugins_url( '/assets/js/admin_myscript.js', __FILE__ ));
}
function frontendEnqueue(){
wp_enqueue_style( 'AtiBlogTestStyle', plugins_url( '/assets/css/front_mystyle.css', __FILE__ ));
wp_enqueue_script( 'AtiBlogTestScript', plugins_url( '/assets/js/front_myscript.js', __FILE__ ));
}
}


if(class_exists('AtiBlogTest')){
$atiblogtest=new AtiBlogTest();
$atiblogtest->register();
}

For css

wp_register_style('style-css',plugin_dir_url(__FILE__).'css/style.css');

for js

 wp_register_script('script-js', plugin_dir_url(__FILE__).'js/script.js',array(), '1.0.0', true);

you can use the css by enqueue them in any page like

wp_enqueue_style('style-css');

you can use the js by enqueue them in any page like

wp_enqueue_script('script-js');