Test Code file for introduction to hooks learnup.php

<?php
/*
Plugin Name: Testing Code
Description: This is just a test plugin for some actions and filters.
Version: 0.1
Author: Con
*/

/**
 * Security measure to prevent direct access.
 * Always add that.
 */
if (! defined('ABSPATH')) {
    exit; // Exit if accessed directly
}

/**
 * This function uses the woocommerce_states filter to modify the states
 * loaded by the variable $states.
 * To test go to your checkout and select United Kingdom,
 * then select Counties.
 */

function wc_uk_counties_add_counties($states)
{
    // redefine the states list for England.
    $states['GB'] = array(
        'AV' => 'Avon',
        'BE' => 'Bedfordshire',
    );
    // Output our new states list for england.
    return $states;
}
// Bind function to filter.
add_filter('woocommerce_states', 'wc_uk_counties_add_counties');

/**
 * This function uses the WordPress core wp_count_posts function
 * to count all posts by type. Our type is 'product'
 *
 */
function woocat_product_count_shortcode()
{
    $count_posts = wp_count_posts('product');
    return $count_posts->publish;
}
// Bind to shortcode [woo_product_count].
add_shortcode('woo_product_count', 'woocat_product_count_shortcode');

/**
 * This function greets the world and prooves you can make the machine talk.
 *
 */
function woocat_hello_world()
{
    echo "Hello World";
}
// Bind to single product page before short description.
add_action('woocommerce_single_product_summary', 'woocat_product_count_shortcode');

/**
 * This function uses PHP core methods to show the IP address.
 *
 */
function come_get_ip()
{
    foreach (array('HTTP_CLIENT_IP', 'HTTP_X_FORWARDED_FOR', 'HTTP_X_FORWARDED', 'HTTP_X_CLUSTER_CLIENT_IP', 'HTTP_FORWARDED_FOR', 'HTTP_FORWARDED', 'REMOTE_ADDR') as $key) {
        if (array_key_exists($key, $_SERVER) === true) {
            foreach (explode(',', $_SERVER[$key]) as $ip) {
                if (filter_var($ip, FILTER_VALIDATE_IP) !== false) {
                    //return $ip;
                    echo $ip . '<br>';
                }
            }
        }
    }
}
// Bind to shortcode [show_ip].
add_shortcode('show_ip', 'come_get_ip');



/**
 * Here are some advanced functions with limited comments.
 *
 */

function custom_notice_for_backorders_allowed()
{
    //instantinate product object
    global $product;

    //check if backorders are allowed
    if ($product->backorders_allowed()) {
        ?>
			Backorders allowed: Put some text and <a href="#">links here.</a>
			<?php
    }
}

// simple output after product title
add_action('woocommerce_single_product_summary', 'simple_output_after_product_titel');



//output after product title
add_action('woocommerce_single_product_summary', 'custom_notice_for_backorders_not_allowed');

function custom_notice_for_backorders_not_allowed()
{
    global $product;

    //check if backorders are not allowed
    if (! $product->backorders_allowed()) {
        ?>
			Backorders not allowed: Put some text and <a href="#">links here.</a>
			<?php
    }
}

// hide coupon field on cart page
function hide_coupon_field_on_cart($enabled)
{
    if (is_cart()) {
        $enabled = false;
    }

    return $enabled;
}
add_filter('woocommerce_coupons_enabled', 'hide_coupon_field_on_cart');

// hide coupon field on checkout page
function hide_coupon_field_on_checkout($enabled)
{
    if (is_checkout()) {
        $enabled = false;
    }

    return $enabled;
}
add_filter('woocommerce_coupons_enabled', 'hide_coupon_field_on_checkout');