Donation notes field example for PMPro Donations.

my_pmprodon_donation_notes.php

<?php
/**
 * Donation notes.
 * Edit the copy below.
 * Add to a custom plugin.
 * Notes are saved into the notes field of the order.
 */
// show the notes field at checkout.
function my_pmprodon_donation_notes() {
	global $pmpro_level;
	
	// check if this level has donations
	$donfields = get_option( 'pmprodon_' . $pmpro_level->id );

	// no donations? just return
	if ( empty( $donfields ) || empty( $donfields['donations'] ) ) {
		return;
	}
	
	// grab data
	if ( ! empty( $_REQUEST['pmpro_donation_notes'] ) ) {
		$pmpro_donation_notes = sanitize_text_field( $_REQUEST['pmpro_donation_notes'] );
	} else {
		$pmpro_donation_notes = '';
	}
	
	// show field and instructions
	?>
	<p class="pmpro_small donation_notes_trigger_p">
	All donations are designated for the general fund. <a href="#" class="donation_notes_trigger">To specify how your donation is used, click here.</a></p>
	<p class="donation_notes_instructions" style="display: none;">Your donation can be earmarked for the general fund, the scholarship fund, or a combination of both. You can also request a specific use for your donation. Let us know in the field below.</p>
	<textarea id="pmpro_donation_notes" name="pmpro_donation_notes" style="display: none;"><?php echo esc_textarea( $pmpro_donation_notes ); ?></textarea>
	<script>
		jQuery(document).ready(function() {
			function show_pmpro_donation_notes() {
				jQuery('#pmpro_donation_notes').show();
				jQuery('p.donation_notes_trigger_p').hide();
				jQuery('p.donation_notes_instructions').show();
			}
			
			jQuery('a.donation_notes_trigger').click(function() {
				show_pmpro_donation_notes();
			});
			
			if ( jQuery('#pmpro_donation_notes').val().length > 0 ) {
				show_pmpro_donation_notes();
			}
		});
	</script>
	<?php
}
add_action( 'pmpro_checkout_after_level_cost', 'my_pmprodon_donation_notes', 15 );

// save donation notes into order notes
function my_pmprodon_save_donation_notes_to_order( $order ) {
	if ( !empty( $_REQUEST['pmpro_donation_notes'] ) ) {
		$value = sanitize_text_field( $_REQUEST['pmpro_donation_notes'] );
	} elseif ( ! empty( $_SESSION['pmpro_donation_notes'] ) ) {
		$value = sanitize_text_field( $_SESSION['pmpro_donation_notes'] );
	} else {
		$value = false;
	}
	
	if ( $value ) {				
		if( !isset( $order->notes ) ) {
			$order->notes = 'Donation Notes: ' . $value . "\n";
		} else {
			$order->notes .= "\nDonation Notes: " . $value . "\n";
		}
	}
	
	return $order;
}
add_filter( 'pmpro_checkout_order', 'my_pmprodon_save_donation_notes_to_order' );

// save notes in session
function my_pmprodon_save_donation_notes_to_session() {
	if ( !empty( $_REQUEST['pmpro_donation_notes'] ) ) {
		$_SESSION['pmpro_donation_notes'] = $_REQUEST['pmpro_donation_notes'];
	}
}
add_action( 'pmpro_checkout_before_processing', 'my_pmprodon_save_donation_notes_to_session' );