Register New Donation Field For Specific Campaign

/**

 * This example shows how to add a new donation field to your site, but

 * only display it in the front-end donation form for a particular campaign.

 *

 * Related examples:

 *

 * @see Register a text field (detailed example) - https://github.com/Charitable/library/blob/master/donation-form/register-new-donation-field-1.5.php

 * @see Register a text field (simple example) - https://github.com/Charitable/library/blob/master/donation-form/collect-national-id-number.php

 * @see Register a checkbox field - https://github.com/Charitable/library/blob/master/donation-form/add-checkbox-field-to-donation-form.php

 * @see Register multiple fields - https://github.com/Charitable/library/blob/master/donation-form/register-multiple-donation-fields.php

 */

/**

 * First of all, we register our new donation field.

 *

 * Also note that the fields will be included in the admin donation

 * form as well. Set admin_form to false if you would like to disable that.

 */

function ed_charitable_register_new_donation_field() {

	/**

	 * Define a new text field.

	 */

	$field = new Charitable_Donation_Field( 'new_text_field', array(

		'label' => __( 'New Text Field', 'charitable' ),

		'data_type' => 'user',

		'donation_form' => array(

			'show_after' => 'phone',

			'required'   => false,

		),

		'admin_form' => true,

		'show_in_meta' => true,

		'show_in_export' => true,

		'email_tag' => array(

			'description' => __( 'The new text field' , 'charitable' ),

		),

	) );

	/**

	 * Register the text field.

	 */

	charitable()->donation_fields()->register_field( $field );

}

add_action( 'init', 'ed_charitable_register_new_donation_field' );

/**

 * Next, remove the custom field from the front-end donation form

 * unless we're donating to a particular campaign.

 *

 * @param  array[] $fields

 * @param  Charitable_Donation_Form $form

 * @return array[]

 */

function ed_charitable_conditionally_show_custom_field( $fields, Charitable_Donation_Form $form ) {

	/**

	 * If you only want to collect a certain field on a certain campaign's

	 * donation form, uncomment this next section and replace 8 with the

	 * ID of your campaign.

	 */

	if ( 8 != $form->get_campaign()->ID ) {

		unset( $fields['new_text_field'] );

	}

	return $fields;

}

add_filter( 'charitable_donation_form_user_fields', 'ed_charitable_conditionally_show_custom_field', 10, 2 );