Sample custom field for EDD FES

gistfile1.phtml

<?php

// Begin FES integration
// add button to the post button listing
function fes_shipping_field_button( $title ) {
	if ( version_compare( fes_plugin_version, '2.2', '>=' ) ) {
	echo  '<button class="fes-button button" data-name="edd_simple_shipping" data-type="action" title="' . $title . '">'. __( 'Shipping', 'edd-simple-shipping' ) . '</button>';
	}
}
add_action('fes_custom_post_button', 'fes_shipping_field_button');

function fes_admin_field_save( $field_id, $label = "", $values = array() ) {
	if( ! isset( $values['label'] ) ) {
		$values['label'] = __( 'Shipping', 'edd-simple-shipping' );
	}

	$values['no_css']  = true;
	$values['is_meta'] = true;
	$values['name']    = 'edd_simple_shipping';
	?>
	<li class="edd_simple_shipping">
		<?php FES_Formbuilder_Templates::legend( $values['label'] ); ?>
		<?php FES_Formbuilder_Templates::hidden_field( "[$field_id][input_type]", 'edd_simple_shipping' ); ?>
		<?php FES_Formbuilder_Templates::hidden_field( "[$field_id][template]", 'edd_simple_shipping' ); ?>
		<div class="fes-form-holder">
			<?php FES_Formbuilder_Templates::common( $field_id, 'edd_simple_shipping', false, $values ); ?>
		</div> <!-- .fes-form-holder -->
	</li>
	<?php
}
add_action( 'fes_admin_field_edd_simple_shipping', 'fes_admin_field_save', 10, 3);

function edd_simple_shipping_formbuilder_is_custom_field( $bool, $template_field ) {
	if ( $bool ) {
		return $bool;
	} else if ( isset( $template_field['template'] ) && $template_field['template'] == 'edd_simple_shipping' ) {
		return true;
	} else {
		return $bool;
	}
}
add_filter('fes_formbuilder_custom_field', 'edd_simple_shipping_formbuilder_is_custom_field', 10, 2);

function edd_simple_shipping_save_custom_fields( $post_id ) {
	if ( isset( $_POST ['edd_simple_shipping'] ) ) {
		$domestic      = ! empty( $_POST ['edd_simple_shipping']['domestic'] ) ? edd_sanitize_amount( $_POST ['edd_simple_shipping']['domestic'] ) : 0;
		$international = ! empty( $_POST ['edd_simple_shipping']['international'] ) ? edd_sanitize_amount( $_POST ['edd_simple_shipping']['international'] ) : 0;
		update_post_meta( $post_id, '_edd_enable_shipping', '1' );
		update_post_meta( $post_id, '_edd_shipping_domestic', $domestic );
		update_post_meta( $post_id, '_edd_shipping_international', $international );
	} else {
		delete_post_meta( $post_id, '_edd_enable_shipping' );
	}
}
add_action( 'fes_submission_form_save_custom_fields', 'edd_simple_shipping_save_custom_fields' );

function edd_simple_shipping_field( $attr, $post_id, $type ) {

	if ( isset( $attr['required'] ) && $attr['required'] == 'yes' ) {
		$required = apply_filters( 'fes_required_class', ' edd-required-indicator', $attr );
	}

	$enabled       = get_post_meta( $post_id, '_edd_enable_shipping', true );
	$domestic      = get_post_meta( $post_id, '_edd_shipping_domestic', true );
	$international = get_post_meta( $post_id, '_edd_shipping_international', true );

	?>
	<div class="fes-fields <?php echo sanitize_key( $attr['name']); ?>">
		<label for="edd_simple_shipping[enabled]">
			<input type="checkbox" name="edd_simple_shipping[enabled]" id="edd_simple_shipping[enabled]" value="1"<?php checked( '1', $enabled ); ?>/>
			<?php _e( 'Enable Shipping', 'edd-simple-shipping' ); ?>
		</label>
		<input class="textfield<?php echo esc_attr( $required ); ?>" id="edd_simple_shipping[domestic]" type="text" data-required="<?php echo $attr['required'] ?>" data-type="text" name="<?php echo esc_attr( $attr['name'] ); ?>[domestic]" placeholder="<?php echo __( 'Enter the domestic shipping charge amount', 'edd-simple-shipping' ); ?>" value="<?php echo esc_attr( $domestic ) ?>" size="10" />
		<input class="textfield<?php echo esc_attr( $required ); ?>" id="edd_simple_shipping[international]" type="text" data-required="<?php echo $attr['required'] ?>" data-type="text" name="<?php echo esc_attr( $attr['name'] ); ?>[international]" placeholder="<?php echo __( 'Enter the international shipping charge amount', 'edd-simple-shipping' ); ?>" value="<?php echo esc_attr( $international ) ?>" size="10" />
	</div> <!-- .fes-fields -->
	<?php
}
add_action('fes_render_field_edd_simple_shipping', 'edd_simple_shipping_field', 10, 3 );