Sometimes, the types of fields that are available by default in Contact Form 7 are just not enough. And sometimes, you want to just be able to use a shortcode when you define the form . For such situation, we can use the wpcf7_add_shortcode() function, combined with the wpcf7_init hook.

Documentation

The wpcf7_add_shortcode() function takes 3 arguments:

• $shortcode, which is our shortcode name, exactly as in WordPress;
• $callback, which is a function that will be called when the shortcode is encountered, exactly as in WordPress;
• $has_name_part, which is boolean and false by default, but if it is set to true, then the shortcode can be used with a name, for example: '[my_shortcode field-name]', just how you would use a usual CF7 field: '[text* your-name]'

Find all details on the Contact Form 7 site’s documentation page: Adding a custom form-tag.

Example

add_action( 'wpcf7_init', 'create_my_custom_cf7_shortcodes' );

function create_my_custom_cf7_shortcodes(){
    wpcf7_add_shortcode( 'lots_of_checkboxes', 'render_checkboxes' );
}

function render_checkboxes(){
    // Construct checkboxes HTML here...
    return $html;
}

Now we can use this when we are defining the form fields: [lots_of_checkboxes], which will output whatever the render_checkboxes() function decides.