Examples WordPress of Hooks in Action

More than 200 hooks exist in WordPress. Below you will find a few examples of common hooks in use.
Register a Custom Menu in the Admin

How to Add and Remove Your Own Functions

If you would like to hook in your own functions, the process is quite simple. You first need to know a few pieces of information. For actions, you’ll want to know the name of the hook, as well as when exactly it runs.

Types of Action and Filter Hooks

The WordPress Codex has two important pages that can help you orient yourself with what hooks are available in WordPress.

WordPress Action Hooks and Filter Hooks

Introduction

This page documents the API (Application Programming Interface) hooks available to WordPress plugin developers, and how to use them.

Does Contact Form 7 support HTML5 input types?

Yes. Contact Form 7 3.4 and higher support form-tags corresponding to these HTML5 input types: email, tel, url, number, range and date.

How to add a contact form into my post content?

Open the settings page for Contact Form 7, and then open the contact form you want to add.

Each contact form has its own tag (shortcode), such as [contact-form-7 id="1234" title="Contact form 1"]. To insert the contact form into your post, copy the shortcode and paste it into the post content.

How to Hide WooCommerce "Free" Price Label

A common WooCommerce question lately has been how to hide the “Free” price label in the product/category/shop pages. Thanks to WooCommerce’s judicious use of filters/actions, this is very easy

How to Set default thumbnails size & creating multiple thumbnail sizes?

Registers a new image size. This means WordPress will create a copy of the image with the specified dimensions when a new image is uploaded.

To set the default Featured Image (formerly Post Thumbnail) dimensions use: set_post_thumbnail_size(). 



<?php add_image_size( $name, $width, $height, $crop ); ?>

if ( function_exists( 'add_theme_support' ) ) {
   add_theme_support( 'post-thumbnails');
   set_post_thumbnail_size( 200, 200, true );
}

What does above code really mean?

Does it mean all my thumbnails will be 800x600 or smaller? Because even after setting set_post_thumbnail_size get_post_thumbnail_id($post->ID) points to full-sized thumbnails (like 2500x1200). I don't really need that big images...

When do WordPress create (custom) thumbnails?

Set the image size by cropping the image (not showing part of it):
Set the image size by resizing the image proportionally (without distorting it):

add_image_size( 'custom-size', 220, 220, array( 'left', 'top' ) ); // Hard crop left top

When setting a crop position, the first value in the array is the x axis crop position, the second is the y axis crop position.

• x_crop_position accepts 'left' 'center', or 'right'.
• y_crop_position accepts 'top', 'center', or 'bottom'.

By default, these values default to 'center' when using hard crop mode.

if ( function_exists( 'add_theme_support' ) ) {
  add_theme_support( 'post-thumbnails');
  set_post_thumbnail_size( 900, 600, true );
  add_image_size( 'foo', 400, 300, true );
  add_image_size( 'bar', 200, 250, true ); 
}

When are these custom thumbnails created (like image-900x600.jpg / image-400x300.jpg etc.) ? Only during upload process? What if I'm just changing themes to theme based on add_image_size functions with different thumbnail sizes, do I have to reupload all my images to get right sizes? If yes, then using timthumb over add_image_size wasn't that bad idea..

How to set different thumbnail sizes per custom post type?

Registers a new image size. This means WordPress will create a copy of the image with the specified dimensions when a new image is uploaded.
To set the default Featured Image (formerly Post Thumbnail) dimensions use: set_post_thumbnail_size().

Usage

<?php add_image_size( $name, $width, $height, $crop ); ?>

if you have multiple post types, maybe this will help
(not tested)(in the loop)

<?php
$post_type = get_post_type(); // get's the post type of a post in the loop
$args=array(
  'public'   => true,
  '_builtin' => false
);
$output = 'names'; // names or objects
$operator = 'and'; // 'and' or 'or'
$post_types = get_post_types($args,$output,$operator); // gets all post types you registered
$post_types = array_values($post_types); // makes it a numerically indexed array

if(in_array( $post_type, $post_types)){ // post is a custom post type -> show post type size thumbnail
  $custom_post_thumbnail = get_the_post_thumbnail($post->ID, $post_type.'-thumbnail');
  if($custom_post_thumbnail != ''){ // there is a custom post thumbnail size
    echo $custom_post_thumbnail;
  } else { // no custom post thumbnail size -> show normal thumbnail
    echo get_the_post_thumbnail($post->ID);
  }
} else { // show normal thumbnail for posts and pages
  echo get_the_post_thumbnail($post->ID);
}
?>

You still have to add the image sizes manually in your theme's functions.php

If you have custom post types review and movies:

add_image_size( 'review-thumbnail', 150, 200, true );
add_image_size( 'movies-thumbnail', 400, 9999 );

How to Display Featured Post with Thumbnails Without Plugin in Homepage

On home page, we generally show a fixed number of recent posts with summary. Although, WordPress provides Sticky Posts functionality but not so useful when number of featured posts are more. So I decided to implement this without any plugin.

1. Display featured post with thumbnail.
2. Title will be placed below the thumbnail.
3. Featured posts will be randomly selected and must show default thumbnail if no thumbnail is defined for the post.
4. All selected posts must appear together, no slider to navigate.
5. It must not use any script(Not good for SEO) or plugin.

1. To implement this, First, You need to create a category (say featuredcategory) and add featured posts in the category.
2. Write following code in function.php of your WordPress theme.

<?php

function getFeaturePosts(){

 ?>             

                <ul class="related-posts">

                <?php

                $default_thumbnail = 'http://img.techbrij.com/techbrij%20logo.gif';

                $the_query = new WP_Query('showposts=5&orderby=rand&category_name=featuredcategory');

                while ($the_query->have_posts()) : $the_query->the_post(); ?>

                        <li>

                             <div class="related_thumbnail">

            <a href="<?php the_permalink() ?>" rel="bookmark" title="<?php the_title_attribute(); ?>">                           

                            <?php

                            if (has_post_thumbnail()):

                             the_post_thumbnail();

                            else:

                            ?>

                            <img src="<?php echo $default_thumbnail; ?>" alt="<?php the_title(); ?>" />

                            <?php endif; ?>

                            </a>

        </div>

        <div style="clear:both;"></div>

            <div class="related_permalink">

            <a href="<?php the_permalink() ?>" rel="bookmark" title="<?php the_title_attribute(); ?>"><?php the_title(); ?></a>      

        </div>

                             

                        </li>            

 

                <?php endwhile; ?>

                <?php wp_reset_query(); ?>

                </ul>

<?php

}

 ?>




In the above code, you need to define $default_thumbnail parameter and assign default thumbnail link. If there is no thumbnail then defined $default_thumbnail link will be displayed.
Following line is the most important line.
$the_query = new WP_Query(‘showposts=5&orderby=rand&category_name=featuredcategory’);
showposts=5: define number of posts to be displayed
orderby=rand: posts are randomly selected
category_name=featuredcategory: define category of featured posts.
3. Add following styles in your css file:

?

/* Related OR Feature Posts */ .related-posts {     list-style:none;     margin:0;     padding:0;           }    .related-posts li {     display:block;     text-align:center;     float:left;     margin:0 auto;     padding-left:3px 10px 3px 0px;        width:150px;     height:175px; } .related-posts li :hover{   } .related_permalink{       text-align:center;     padding-top:5px;        padding-bottom:5px; margin-bottom:2px;    }  .related_permalink a{ color:black; font-weight:bold;  text-decoration:none;  }  .related_permalink a:hover{  text-decoration:underline;  } .related_thumbnail{      text-align:center; } .related_thumbnail img { border-width:0px; width:100px; float:none; margin:0 auto; } /* Related Posts End */

you can change thumbnail size by defining height and width in .related_thumbnail img style.
4. Now call method where you want to display featured posts.

?

<?php  getFeaturePosts(); ?>

See following sample display of featured posts: