[Plugin] Funções adicionais ao functions.php

Mover o Bar do Admin para o rodapé

function stick_admin_bar_to_bottom_css() {
        echo "
        <style type='text/css'>
        html {
                padding-bottom: 28px !important;
        }

        body {
                margin-top: -28px;
        }

        #wpadminbar {
                top: auto !important;
                bottom: 0;
        }

        #wpadminbar .quicklinks .menupop ul {
                bottom: 28px;
        }
        </style>
        ";
}

add_action('admin_head', 'stick_admin_bar_to_bottom_css');
add_action('wp_head', 'stick_admin_bar_to_bottom_css');

Fonte: wpbeginner

Resumo com apenas 100 palavras

function minWord($content)
{
	global $post;
	$content = $post->post_excerpt;
	if (str_word_count($content) < 100 ) //set this to the minimum number of words
	wp_die( __('Error: your post is below the minimum word count. It needs to be longer than 100 words.') );
}
add_action('publish_post', 'minWord');

Fonte: wpbeginner

Adicionar filtro ao custom fields

add_filter( 'parse_query', 'ba_admin_posts_filter' );
add_action( 'restrict_manage_posts', 'ba_admin_posts_filter_restrict_manage_posts' );
function ba_admin_posts_filter( $query )
{
    global $pagenow;
    if ( is_admin() && $pagenow=='edit.php' && isset($_GET['ADMIN_FILTER_FIELD_NAME']) && $_GET['ADMIN_FILTER_FIELD_NAME'] != '') {
        $query->query_vars['meta_key'] = $_GET['ADMIN_FILTER_FIELD_NAME'];
    if (isset($_GET['ADMIN_FILTER_FIELD_VALUE']) && $_GET['ADMIN_FILTER_FIELD_VALUE'] != '')
        $query->query_vars['meta_value'] = $_GET['ADMIN_FILTER_FIELD_VALUE'];
    }
}
function ba_admin_posts_filter_restrict_manage_posts()
{
    global $wpdb;
    $sql = 'SELECT DISTINCT meta_key FROM '.$wpdb->postmeta.' ORDER BY 1';
    $fields = $wpdb->get_results($sql, ARRAY_N);
?>
<select name="ADMIN_FILTER_FIELD_NAME">
<option value=""><?php _e('Filter By Custom Fields', 'baapf'); ?></option>
<?php
    $current = isset($_GET['ADMIN_FILTER_FIELD_NAME'])? $_GET['ADMIN_FILTER_FIELD_NAME']:'';
    $current_v = isset($_GET['ADMIN_FILTER_FIELD_VALUE'])? $_GET['ADMIN_FILTER_FIELD_VALUE']:'';
    foreach ($fields as $field) {
        if (substr($field[0],0,1) != "_"){
        printf
            (
                '<option value="%s"%s>%s</option>',
                $field[0],
                $field[0] == $current? ' selected="selected"':'',
                $field[0]
            );
        }
    }
?>
</select> <?php _e('Value:', 'baapf'); ?><input type="TEXT" name="ADMIN_FILTER_FIELD_VALUE" value="<?php echo $current_v; ?>" />
<?php
}

fonte: wpsnipp

Como remover links da barra de administração(topo) do Wp

function remove_admin_bar_links() {
    global $wp_admin_bar;
    $wp_admin_bar->remove_menu('wp-logo');          // Remove the WordPress logo
    $wp_admin_bar->remove_menu('about');            // Remove the about WordPress link
    $wp_admin_bar->remove_menu('wporg');            // Remove the WordPress.org link
    $wp_admin_bar->remove_menu('documentation');    // Remove the WordPress documentation link
    $wp_admin_bar->remove_menu('support-forums');   // Remove the support forums link
    $wp_admin_bar->remove_menu('feedback');         // Remove the feedback link
    $wp_admin_bar->remove_menu('site-name');        // Remove the site name menu
    $wp_admin_bar->remove_menu('view-site');        // Remove the view site link
    $wp_admin_bar->remove_menu('updates');          // Remove the updates link
    $wp_admin_bar->remove_menu('comments');         // Remove the comments link
    $wp_admin_bar->remove_menu('new-content');      // Remove the content link
    $wp_admin_bar->remove_menu('w3tc');             // If you use w3 total cache remove the performance link
    $wp_admin_bar->remove_menu('my-account');       // Remove the user details tab
}
add_action( 'wp_before_admin_bar_render', 'remove_admin_bar_links' );

Fonte: paulund

otimas dicas

Restringir o upload de arquivos

<?php
/**
 * Plugin Name: Restrict mime types
 * Plugin URI:  http://wpengineer.com/?p=2369
 * Description: Restrict list of allowed mime types and file extensions.
 * Version:     1.0.0
 * License:     GPLv3
 * Author:      Frank Bültge
 * Author URI:  http://bueltge.de/
 */
 // This file is not called from WordPress. We don't like that.
! defined( 'ABSPATH' ) and exit;
// If the function exists this file is called as upload_mimes.
// We don't do anything then.
if ( ! function_exists( 'fb_restrict_mime_types' ) ) {
	add_filter( 'upload_mimes', 'fb_restrict_mime_types' );
	/**
	 * Retrun allowed mime types
	 *
	 * @see     function get_allowed_mime_types in wp-includes/functions.php
	 * @param   array Array of mime types
	 * @return  array Array of mime types keyed by the file extension regex corresponding to those types.
	 */
	function fb_restrict_mime_types( $mime_types ) {
		$mime_types = array(
			'pdf' => 'application/pdf',
			'doc|docx' => 'application/msword',
		);
		return $mime_types;
	}
}
// If the function exists this file is called as post-upload-ui.
// We don't do anything then.
if ( ! function_exists( 'fb_restrict_mime_types_hint' ) ) {
	// add to wp
	add_action( 'post-upload-ui', 'fb_restrict_mime_types_hint' );
	/**
	 * Get an Hint about the allowed mime types
	 *
	 * @return  void
	 */
	function fb_restrict_mime_types_hint() {
		echo '<br />';
		_e( 'Accepted MIME types: PDF, DOC/DOCX' );
	}
}

Fonte: wpengineer.com

Substitua reticências por um permalink

function replace_excerpt($content) {
       return str_replace('[...]',
               '... <div class="more-link"><a href="'. get_permalink() .'">Continue Reading</a></div>',
               $content
       );
}
add_filter('the_excerpt', 'replace_excerpt');

Fonte: wprecipes.com

Encurtar titulos

No functions.php:

function short_title($after = '', $length) {
	$mytitle = get_the_title();
	if ( strlen($mytitle) > $length ) {
	$mytitle = substr($mytitle,0,$length);
	echo $mytitle . $after;
	} else {
	echo $mytitle;
	}
}

Em seu template:
<?php short_title('...', 40); ?>