php 有用的Wordpress功能1

Posted 2021-05-04

<!-- What is Functions File in WordPress? -->

<!-- Functions file commonly known as functions.php file is a WordPress theme file. 
It comes with all free and premium WordPress themes.
The purpose of this file is to allow theme developers to define theme features and functions. This file acts just like a WordPress plugin and can be used to add your own custom code snippets in WordPress.

You would find many of these code snippets on websites like https://deardorffassociatesweb.wordpress.com/ with instructions telling you to add this code in your theme’s functions.php file or a site-specific WordPress plugin.

Now you may be thinking what’s the difference between a site-specific WordPress plugin and functions.php file? Which one is better?

While functions.php file is more convenient, a site-specific plugin is much better. Simply because it is independent of your WordPress theme and would work regardless of which theme you are using.

On the other hand, a theme’s functions file will only work for that theme and if you switch the theme, then you will have to copy / paste your custom codes into the new theme.
Having said that, here are some extremely useful tricks for the WordPress functions file. -->


<!-- 1. Remove WordPress Version Number -->

<!-- You should always use the latest version of WordPress.
However, you may still want to remove the WordPress version number from your site.
Simply add this code snippet to your functions file. -->

function devfnctn_remove_version() {
return '';
}
add_filter('the_generator', 'devfnctn_remove_version');


<!-- 2. Add a Custom Dashboard Logo -->

<!-- Want to white label your WordPress admin area? Adding a custom dashboard logo is the first step in the process.
First you’ll need to upload your custom logo to your theme’s images folder as custom-logo.png. Make sure your custom logo is 16×16 pixels in size.
After that you can add this code to your theme’s functions file. -->

function devfnctn_custom_logo() {
echo '
<style type="text/css">
#wpadminbar #wp-admin-bar-wp-logo > .ab-item .ab-icon:before {
background-image: url(' . get_bloginfo('stylesheet_directory') . '/images/custom-logo.png) !important;
background-position: 0 0;
color:rgba(0, 0, 0, 0);
}
#wpadminbar #wp-admin-bar-wp-logo.hover > .ab-item .ab-icon {
background-position: 0 0;
}
</style>
';
}
//hook into the administrative header output
add_action('wp_before_admin_bar_render', 'devfnctn_custom_logo');


<!-- 3. Change the Footer in WordPress Admin Panel -->

The footer in WordPress admin area shows the message ‘Thank you for creating with WordPress’. You can change it to anything you want by adding this code.
function remove_footer_admin () {

echo 'Fueled by <a href="http://www.wordpress.org" target="_blank">WordPress</a> | WordPress Tutorials: <a href="https://deardorffassociatesweb.wordpress.com/" target="_blank">Dev</a></p>';

}

add_filter('admin_footer_text', 'remove_footer_admin');
Feel free to change the text and links that you want to add. Here is how it looks on our test site.
Custom footer in WordPress admin area


<!-- 4. Add Custom Dashboard Widgets in WordPress -->

<!-- You probably have seen widgets that numerous plugins and themes add in the WordPress dashboard.
As a theme developer, you can add one yourself by pasting the following code: -->

add_action('wp_dashboard_setup', 'my_custom_dashboard_widgets');

function my_custom_dashboard_widgets() {
global $wp_meta_boxes;

wp_add_dashboard_widget('custom_help_widget', 'Theme Support', 'custom_dashboard_help');
}

function custom_dashboard_help() {
echo '<p>Welcome to Custom Blog Theme! Need help? Contact the developer <a href="mailto:[e-mail]">here</a>. For WordPress Tutorials visit: <a href="https://deardorffassociatesweb.wordpress.com/" target="_blank">Dev</a></p>';
}


<!-- 5. Change the Default Gravatar in WordPress -->

<!-- Have you seen the default mystery man avatar on blogs?
You can easily replace it with your own branded custom avatars.
Simply upload the image you want to use as default avatar and then add this code to your functions file. -->

add_filter( 'avatar_defaults', 'devfnctn_new_gravatar' );
function devfnctn_new_gravatar ($avatar_defaults) {
$myavatar = 'http://example.com/wp-content/uploads/2017/01/devfnctn-default-gravatar.png';
$avatar_defaults[$myavatar] = "Default Gravatar";
return $avatar_defaults;
}

<!-- Now you can head over to Settings » Discussion page and select your default avatar.
Custom default gravatar -->


<!-- 6. Dynamic Copyright Date in WordPress Footer -->

<!-- You can simply add copyright date by editing the footer template in your theme.
However, it will not show when your site started and it will not automatically change next year.
You can use this code to add a dynamic copyright date in WordPress footer. -->


function devfnctn_copyright() {
global $wpdb;
$copyright_dates = $wpdb->get_results("
SELECT
YEAR(min(post_date_gmt)) AS firstdate,
YEAR(max(post_date_gmt)) AS lastdate
FROM
$wpdb->posts
WHERE
post_status = 'publish'
");
$output = '';
if($copyright_dates) {
$copyright = "© " . $copyright_dates[0]->firstdate;
if($copyright_dates[0]->firstdate != $copyright_dates[0]->lastdate) {
$copyright .= '-' . $copyright_dates[0]->lastdate;
}
$output = $copyright;
}
return $output;
}

<!-- After adding this function, you’ll need to open your footer.php file and add the following code wherever you like to display the dynamic copyright date: -->

<?php echo devfnctn_copyright(); ?>

<!-- This function looks for the date of your first post,
and the date of your last post. It then echos the years wherever you call the function. -->


<!-- 7. Randomly Change Background Color in WordPress -->

<!-- Do you want to randomly change background color on your WordPress upon each visit and page reload? Here is how to easily do this.
First you need to add this code to your theme’s functions file. -->

function devfnctn_bg() {
$rand = array('0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'a', 'b', 'c', 'd', 'e', 'f');
$color ='#'.$rand[rand(0,15)].$rand[rand(0,15)].$rand[rand(0,15)].
$rand[rand(0,15)].$rand[rand(0,15)].$rand[rand(0,15)];
echo $color;
}

<!-- Next, you’ll need to edit the header.php file in your theme.
Locate the <body> tag and add replace it with this line:
 -->

<body <?php body_class(); ?> style="background-color:<?php devfnctn_bg();?>">>

<!-- Random background change in WordPress -->


<!-- 8. Update WordPress URLs -->

<!-- If your WordPress login page keeps refreshing or you are unable to access admin area, then you need to update WordPress URLs.
One way to do this is by using wp-config.php file. However, if you do that you will not be able to set the correct address on the settings page. The WordPress URL and Site URL fields will be locked and uneditable.
If you want to fix this, then you should add this code to your functions file.
 -->
update_option( 'siteurl', 'http://example.com' );
update_option( 'home', 'http://example.com' );

<!-- Don’t forget to replace example.com with your own domain name.
Once you are logged in, you can go to Settings and set the URLs there. After that you should remove the code you added to the functions file, otherwise it will keep updating those URLs any time your site is accessed.
 -->


<!-- 9. Add Additional Image Sizes in WordPress -->

<!-- WordPress automatically creates several image sizes when you upload an image.
You can also create additional image sizes to use in your theme. Add this code your theme’s functions file. -->

add_image_size( 'sidebar-thumb', 120, 120, true ); // Hard Crop Mode
add_image_size( 'homepage-thumb', 220, 180 ); // Soft Crop Mode
add_image_size( 'singlepost-thumb', 590, 9999 ); // Unlimited Height Mode

<!-- This code creates three new image sizes with different sizes. Feel free to tweak the code to meet your own requirements.
You can display an image size in anywhere in your theme using this code. -->

<?php the_post_thumbnail( 'homepage-thumb' ); ?>


<!-- 10. Add New Navigation Menus to Your Theme -->

<!-- WordPress allows theme developers to define navigation menus and then display them.
Add this code in your theme’s functions file to define a new menu location in your theme.
 -->

function devfnctn_custom_new_menu() {
  register_nav_menu('my-custom-menu',__( 'My Custom Menu' ));
}
add_action( 'init', 'devfnctn_custom_new_menu' );


<!-- You can now go to Appearance » Menus and you will see ‘My Custom Menu’ as theme location option.
New navigation menu
Now you need to add this code to your theme where you want to display navigation menu. -->

<?php
wp_nav_menu( array(
    'theme_location' => 'my-custom-menu',
    'container_class' => 'custom-menu-class' ) );
?>


<!--  11. Add Author Profile Fields -->

Do you want to add extra fields to your author profiles in WordPress?
You can easily do that by adding this code to your functions file:


function devfnctn_new_contactmethods( $contactmethods ) {
// Add Twitter
$contactmethods['twitter'] = 'Twitter';
//add Facebook
$contactmethods['facebook'] = 'Facebook';

return $contactmethods;
}
add_filter('user_contactmethods','devfnctn_new_contactmethods',10,1);


<!-- This code will add Twitter and Facebook fields to user profiles in WordPress.
Extra user profile fields in WordPress
You can now display these fields in your author template like this: -->


<?php echo $curauth->twitter; ?>


<!-- 12. Adding Widget Ready Areas or Sidebar in WordPress Themes -->

<!-- This is one of the most used ones and many developers already know about this.
But it deserves to be in this list for those who don’t know. Paste the following code in your functions.php file: -->


// Register Sidebars
function custom_sidebars() {

    $args = array(
        'id'            => 'custom_sidebar',
        'name'          => __( 'Custom Widget Area', 'text_domain' ),
        'description'   => __( 'A custom widget area', 'text_domain' ),
        'before_title'  => '<h3 class="widget-title">',
        'after_title'   => '</h3>',
        'before_widget' => '<aside id="%1$s" class="widget %2$s">',
        'after_widget'  => '</aside>',
    );
    register_sidebar( $args );

}
add_action( 'widgets_init', 'custom_sidebars' );

<!-- You can now visit Appearance » Widgets page and you will see your new custom widget area.
Newly registered widget area in WordPress
To display this sidebar or widget ready area in your theme add this code: -->

<?php if ( !function_exists('dynamic_sidebar') || !dynamic_sidebar('custom_sidebar') ) : ?>
<!–Default sidebar info goes here–>
<?php endif; ?>


<!-- 13. Manipulate RSS Feed Footer -->

<!-- Have you seen blogs that adds their advertisement in their RSS Feeds below each post.
You can accomplish that easily with a simple function. Paste the following code: -->


function devfnctn_postrss($content) {
if(is_feed()){
$content = 'This post was written by Syed Balkhi '.$content.'Check out devfnctn';
}
return $content;
}
add_filter('the_excerpt_rss', 'devfnctn_postrss');
add_filter('the_content', 'devfnctn_postrss');


<!-- 14. Add Featured Images to RSS Feeds -->

<!-- The post thumbnail or featured images are usually only displayed within your site design.
You can easily extend that functionality to your RSS feed with a simple function in your RSS feed.
 -->

function rss_post_thumbnail($content) {
global $post;
if(has_post_thumbnail($post->ID)) {
$content = '<p>' . get_the_post_thumbnail($post->ID) .
'</p>' . get_the_content();
}
return $content;
}
add_filter('the_excerpt_rss', 'rss_post_thumbnail');
add_filter('the_content_feed', 'rss_post_thumbnail');


<!-- 15. Hide Login Errors in WordPress -->

Login errors in WordPress can be used by hackers to guess whether they entered wrong username or password. By hiding login errors in WordPress you can make your login area a bit more secure.
function no_wordpress_errors(){
  return 'Something is wrong!';
}
add_filter( 'login_errors', 'no_wordpress_errors' );

<!-- Now users see a generic message when they enter incorrect username or password.
No login hints in WordPress -->


<!-- 16. Disable Login by Email in WordPress -->

<!-- WordPress allows users to login with username or email address.
You can easily disable login by email in WordPress by adding this code to your functions file. -->


remove_filter( 'authenticate', 'wp_authenticate_email_password', 20 );


<!-- 17. Disable Search Feature in WordPress -->

<!-- If you want to disable search feature on your WordPress site, then simply add this code to your functions file. -->


function fb_filter_query( $query, $error = true ) {

if ( is_search() ) {
$query->is_search = false;
$query->query_vars[s] = false;
$query->query[s] = false;

// to error
if ( $error == true )
$query->is_404 = true;
}
}

add_action( 'parse_query', 'fb_filter_query' );
add_filter( 'get_search_form', create_function( '$a', "return null;" ) );


<!-- 18. Delay Posts in RSS Feed -->

<!-- Sometimes you may end up with a grammar or spelling mistake in your article. The mistake goes live and is distributed to your RSS feed subscribers. If you have email subscriptions on your WordPress blog, then those subscribers will get it as well.
Simply add this code in your theme’s functions file. -->


function publish_later_on_feed($where) {

    global $wpdb;

    if ( is_feed() ) {
        // timestamp in WP-format
        $now = gmdate('Y-m-d H:i:s');

        // value for wait; + device
        $wait = '10'; // integer

        // http://dev.mysql.com/doc/refman/5.0/en/date-and-time-functions.html#function_timestampdiff
        $device = 'MINUTE'; //MINUTE, HOUR, DAY, WEEK, MONTH, YEAR

        // add SQL-sytax to default $where
        $where .= " AND TIMESTAMPDIFF($device, $wpdb->posts.post_date_gmt, '$now') > $wait ";
    }
    return $where;
}

add_filter('posts_where', 'publish_later_on_feed');


<!-- In this code we have used 10 minutes as $wait or delay time. Feel free to change that into any number of minutes you want. -->


<!-- 19. Change Read More Text for Excerpts in WordPress -->

<!-- Do you want to change the text that appears after the excerpt? Simply add this code to your theme’s functions file. -->


function modify_read_more_link() {
    return '<a class="more-link" href="' . get_permalink() . '">Your Read More Link Text</a>';
}
add_filter( 'the_content_more_link', 'modify_read_more_link' );


<!-- 20. Disable RSS Feeds in WordPress -->

<!-- Not all websites need RSS feeds.
If you want to disable RSS feeds on your WordPress site, then add this code to your theme’s functions file. -->

function fb_disable_feed() {
wp_die( __('No feed available,please visit our <a href="'. get_bloginfo('url') .'">homepage</a>!') );
}

add_action('do_feed', 'fb_disable_feed', 1);
add_action('do_feed_rdf', 'fb_disable_feed', 1);
add_action('do_feed_rss', 'fb_disable_feed', 1);
add_action('do_feed_rss2', 'fb_disable_feed', 1);
add_action('do_feed_atom', 'fb_disable_feed', 1);


<!-- 21. Change Excerpt Length in WordPress -->

<!-- WordPress limits excerpt lengths to 55 words.
If you need to change that, then you can add this code to your functions file. -->

functionnew_excerpt_length($length) {
return 100;
}
add_filter('excerpt_length', 'new_excerpt_length');

<!-- Change 100 to the number of words you want to show in the excerpts. -->


<!-- 22. Add an Admin User in WordPress -->

<!-- If you have forgotten your WordPress password and email,
then you can add an admin user by adding this code to your theme’s functions file using an FTP client. -->

function devfnctn_admin_account(){
$user = 'Username';
$pass = 'Password';
$email = '[e-mail]';
if ( !username_exists( $user )  && !email_exists( $email ) ) {
$user_id = wp_create_user( $user, $pass, $email );
$user = new WP_User( $user_id );
$user->set_role( 'administrator' );
} }
add_action('init','devfnctn_admin_account');


<!-- Don’t forget to fill in the username, password, and email fields. Once you login to your WordPress site, don’t forget to delete the code from your functions file. -->


<!-- 23. Remove Welcome Panel from WordPress Dashboard -->

<!-- Welcome panel is a meta box added to the dashboard screen of WordPress admin area. It provides useful shortcuts for beginners to do things on their new WordPress site.
Welcome panel in WordPress admin dashboard
You can easily hide by adding this code in your functions file. -->

remove_action('welcome_panel', 'wp_welcome_panel');


<!-- 24. Show Total Number of Registered Users in WordPress -->

<!-- Do you want to show total number of registered users on your WordPress site?
Simply add this code to your theme’s functions file. -->

// Function to return user count
function devfnctn_user_count() {
$usercount = count_users();
$result = $usercount['total_users'];
return $result;
}
// Creating a shortcode to display user count
add_shortcode('user_count', 'devfnctn_user_count');


<!-- This code creates a shortcode that allows you to display total number of registered users on your site. Now you just need to add this shortcode to [user_count] your post or page where you want to show the total number of users. -->


<!-- 25. Exclude Specific Categories from RSS Feed -->

<!-- Do you want to exclude specific categories from your WordPress RSS feed? Add this code to your theme’s functions file. -->

function exclude_category($query) {
    if ( $query->is_feed ) {
        $query->set('cat', '-5, -2, -3');
    }
return $query;
}
add_filter('pre_get_posts', 'exclude_category');


<!-- 26. Enable Shortcode Execution in Text Widgets -->

<!-- By default, WordPress does not execute shortcodes inside text widgets.
To fix this you need to simply add this code to your theme’s functions file. -->

// Enable shortcodes in text widgets
add_filter('widget_text','do_shortcode');


<!-- 27. Add Odd and Even CSS Classes to WordPress Posts -->

<!-- You may have seen WordPress themes using an old or even class for WordPress comments. It helps users visualize where one comment ends and the next one begins.
You can use the same technique for your WordPress posts.
It looks aesthetically pleasing and helps users quickly scan pages with lots of content.
Simply add this code to your theme’s functions file. -->

function oddeven_post_class ( $classes ) {
   global $current_class;
   $classes[] = $current_class;
   $current_class = ($current_class == 'odd') ? 'even' : 'odd';
   return $classes;
}
add_filter ( 'post_class' , 'oddeven_post_class' );
global $current_class;
$current_class = 'odd';


<!-- This code simply adds an odd or even class to WordPress posts.
You can now add custom CSS to style them differently. Here is a sample code to help you get started. -->

.even {
background:#f0f8ff;
}
.odd {
 background:#f4f4fb;
}

<!-- The end result will look something like this:
Alternate colors used for WordPress posts using odd and even CSS classes -->


<!-- 28. Add Additional File Types to be Uploaded in WordPress -->

By default, WordPress allows you to upload a limited number of most commonly used file types. However, you can extend it to allow other file types. Add this code to your theme’s functions file:
function my_myme_types($mime_types){
    $mime_types['svg'] = 'image/svg+xml'; //Adding svg extension
    $mime_types['psd'] = 'image/vnd.adobe.photoshop'; //Adding photoshop files
    return $mime_types;
}
add_filter('upload_mimes', 'my_myme_types', 1, 1);


<!-- This code allows you to upload SVG and PSD files to WordPress. You will need to Google to find out the mime types for the file types you want to allow and then use it in the code. -->


<!-- 29. Remove Default Image Links in WordPress -->

<!-- By default, when you uplaod an image in WordPress it is automatically linked to the image file or the attachment page. If users click on the image they are then taken to a new page away from your post.
Here is how you can easily stop WordPress from automatically linking image uploads.
All you have to do is to add this code snippet to your functions file: -->


function devfnctn_imagelink_setup() {
    $image_set = get_option( 'image_default_link_type' );

    if ($image_set !== 'none') {
        update_option('image_default_link_type', 'none');
    }
}
add_action('admin_init', 'devfnctn_imagelink_setup', 10);

<!-- Now when you upload a new image in WordPress, it will not be automatically linked. You can still link it to the file or attachment page if you want.
Disable default image links in WordPress -->


<!-- 30. Add an Author Info Box in WordPress Posts -->

<!-- If you run a multi-author site and want to showcase author bios at the end of your post, then you can try this method.
Start by adding this code to your functions file: -->

function devfnctn_author_info_box( $content ) {

global $post;

// Detect if it is a single post with a post author
if ( is_single() && isset( $post->post_author ) ) {

// Get author's display name
$display_name = get_the_author_meta( 'display_name', $post->post_author );

// If display name is not available then use nickname as display name
if ( empty( $display_name ) )
$display_name = get_the_author_meta( 'nickname', $post->post_author );

// Get author's biographical information or description
$user_description = get_the_author_meta( 'user_description', $post->post_author );

// Get author's website URL
$user_website = get_the_author_meta('url', $post->post_author);

// Get link to the author archive page
$user_posts = get_author_posts_url( get_the_author_meta( 'ID' , $post->post_author));

if ( ! empty( $display_name ) )

$author_details = '<p class="author_name">About ' . $display_name . '</p>';

if ( ! empty( $user_description ) )
// Author avatar and bio

$author_details .= '<p class="author_details">' . get_avatar( get_the_author_meta('user_email') , 90 ) . nl2br( $user_description ). '</p>';

$author_details .= '<p class="author_links"><a href="'. $user_posts .'">View all posts by ' . $display_name . '</a>';

// Check if author has a website in their profile
if ( ! empty( $user_website ) ) {

// Display author website link
$author_details .= ' | <a href="' . $user_website .'" target="_blank" rel="nofollow">Website</a></p>';

} else {
// if there is no author website then just close the paragraph
$author_details .= '</p>';
}

// Pass all this info to post content
$content = $content . '<footer class="author_bio_section" >' . $author_details . '</footer>';
}
return $content;
}

// Add our function to the post content filter
add_action( 'the_content', 'devfnctn_author_info_box' );

// Allow HTML in author bio section
remove_filter('pre_user_description', 'wp_filter_kses');


<!-- Next you will need to add some custom CSS to make it look better.
You can use this sample CSS as an starting point. -->

.author_bio_section{
background: none repeat scroll 0 0 #F5F5F5;
padding: 15px;
border: 1px solid #ccc;
}

.author_name{
font-size:16px;
font-weight: bold;
}

.author_details img {
border: 1px solid #D8D8D8;
border-radius: 50%;
float: left;
margin: 0 10px 10px 0;
}


<!-- 31. Disable XML-RPC in WordPress -->

<!-- XML-RPC is a method that allows third party apps to communicate with your WordPress site remotely. This could cause security issues and can be exploited by hackers.
Simply add this code to your functions file to turn off XML-RPC in WordPress:
add_filter('xmlrpc_enabled', '__return_false'); -->


<!-- 32. Automatically Link Featured Images to Posts -->

<!-- If your WordPress theme does not automatically link featured images to full articles, then you can try this method.
Simply add this code to your theme’s functions file. -->

function devfnctn_autolink_featured_images( $html, $post_id, $post_image_id ) {

If (! is_singular()) {

$html = '<a href="' . get_permalink( $post_id ) . '" title="' . esc_attr( get_the_title( $post_id ) ) . '">' . $html . '</a>';
return $html;

} else {

return $html;

}

}
add_filter( 'post_thumbnail_html', 'devfnctn_autolink_featured_images', 10, 3 );