How to create custom Divi module?

Most other solutions here are way too complex. The simplest way is to load your custom module in the divi specific action hook et_builder_ready, like this:

add_action( 'et_builder_ready', 'evr_initialize_divi_modules' );function evr_initialize_divi_modules() {    if ( ! class_exists( 'ET_Builder_Module' ) ) { return; }    class EVR_Builder_Module_Testimonial extends ET_Builder_Module {        function init() {            $this->name       = esc_html__( 'Testimonial', 'evr' );            $this->slug       = 'evr_pb_testimonial';            $this->fb_support = true;            // ...        }    }}

You can find the full demo-code on github. Along with some instructions how to get it work in the all new Divi 3 frontend builder:

https://github.com/stracker-phil/divi3-vb-custom-modules/

Place below in your functions.php file. The include file (I called it custom-modules.php) will be a class that extends ET_Builder_Module (which is very similar to WP_Widget). Just open the file from Divi>>includes>>builder>>main-modules.php. Use any of the preexisting modules as an example or basis for your new one. Copy and paste into your custom-modules.php. New class names, make edits as needed, etc.

function doCustomModules(){ if(class_exists("ET_Builder_Module")){    include("custom-modules.php"); }}function prepareCustomModule(){ global $pagenow; $is_admin = is_admin(); $action_hook = $is_admin ? 'wp_loaded' : 'wp'; $required_admin_pages = array( 'edit.php', 'post.php', 'post-new.php', 'admin.php', 'customize.php', 'edit-tags.php', 'admin-ajax.php', 'export.php' ); // list of admin pages where we need to load builder files $specific_filter_pages = array( 'edit.php', 'admin.php', 'edit-tags.php' ); // list of admin pages where we need more specific filtering $is_edit_library_page = 'edit.php' === $pagenow && isset( $_GET['post_type'] ) && 'et_pb_layout' === $_GET['post_type'];    $is_role_editor_page = 'admin.php' === $pagenow && isset( $_GET['page'] ) && 'et_divi_role_editor' === $_GET['page'];    $is_import_page = 'admin.php' === $pagenow && isset( $_GET['import'] ) && 'wordpress' === $_GET['import']; // Page Builder files should be loaded on import page as well to register the et_pb_layout post type properly    $is_edit_layout_category_page = 'edit-tags.php' === $pagenow && isset( $_GET['taxonomy'] ) && 'layout_category' === $_GET['taxonomy']; if ( ! $is_admin || ( $is_admin && in_array( $pagenow, $required_admin_pages ) && ( ! in_array( $pagenow, $specific_filter_pages ) || $is_edit_library_page || $is_role_editor_page || $is_edit_layout_category_page || $is_import_page ) ) ) {    add_action($action_hook, 'doCustomModules', 9789); }}$theme_data = wp_get_theme();$parent_data = $theme_data->parent();if(version_compare((string)$parent_data->Version, "2.5.9", ">")) {    add_action('et_builder_ready', 'doCustomModules');} else {    doCustomModule();}

Important note: The slug for your custom module must contain the string et_pb_, or it will be filtered out by the function et_pb_allowed_modules_list().

I was able to add a new Divi module using the following code (requires PHP 5.3+ for the anonymous function):

add_action(is_admin() ? 'wp_loaded' : 'wp', function() {  require __DIR__ . '/custom-divi-module.php';}, 20);

Inside the included file, copy and paste a class from the wp-content/themes/Divi/includes/builder/main-modules.php file, then modify to suit your needs. See the example below (copy an actual class from the file mentioned to get the content of each method listed below… I like the ET_Builder_Module_Code class for simplicity's sake):

class YOUR_MODULE_NAME extends ET_Builder_Module {  function init() {    // Name, slug, and some other settings for the module go here  }  function get_fields() {    // This method returns an array of fields that the module will    // display as the module settings  }  function shortcode_callback($atts, $content = null, $function_name) {    // This method returns the content the module will display  }}new YOUR_MODULE_NAME;