Another take on the custom fields for maxk97

my_pmpro_rh_custom_fields_maxk97.php

<?php
/**
 * Custom Fields for various sections of checkout
 */
function my_pmpro_rh_custom_fields() {
	global $current_user;

	// don't break if Register Helper is not loaded
	if ( ! function_exists( 'pmprorh_add_registration_field' ) ) {
		return false;
	}

	if ( ! pmpro_hasMembershipLevel() || current_user_can( 'edit_users' ) ) {
		//pmprorh_add_checkout_box( 'additional', 'Additional Information' );
		
		//How did you hear fields?
		$how_hear_fields = array();

		// how_hear field
		$how_hear_fields[] = new PMProRH_Field(
			'how_hear',
			'select',
			array(
				'label' => 'How did you hear about us?',
				'options' => array(
					'facebook' => 'Facebook',
					'twitter' => 'Twitter',
					'instagram' => 'Instagram',
					'google' => 'Google',
					'promotional leaflet' => 'Promotional Leaflet',
					'magazine advert' => 'Magazine Advert',
					'friend or family' => 'Friend Or Family',
					'other' => 'Other',
				),
				'profile' => 'admins',
				'memberslistcsv' => true,
				'required' => false,
			)
		);
		$how_hear_fields[] = new PMProRH_Field(
			'how_hear_referrer',
			'text',
			array(
				'label' => 'Referred by',
				'profile' => 'admins',
				'memberslistcsv' => true,
				'depends' => array(
					array(
						'id' => 'how_hear',
						'value' => 'other',
					),
				),
			)
		);
		foreach ( $how_hear_fields as $how_hear_field ) {
			pmprorh_add_registration_field( 'checkout_boxes', $how_hear_field );
		}
	}

	// Gender and DOB fields
	$gender_dob_fields = array();
    $gender_dob_fields[] = new PMProRH_Field( 'gender', 'select', array(
		'label' => 'Gender',
		'profile' => true,
		'required' => false,
		'memberslistcsv' => true,
		'options' => array(
			'' => '',
			'male' => 'Male',
			'female' => 'Female',
			'non-binary' => 'Non-binary',
		),
	) );
	$gender_dob_fields[] = new PMProRH_Field( 'dob', 'date', array(
		'label' => 'Date of Birth',
		'size' => 40,
		'profile' => true,
		'required' => false,
		'memberslistcsv' => true,
	) );

	//define the fields
	$interests_fields = array();
	
	$interests_fields[] = new PMProRH_Field( ' ', 'html', array( 'html' => '<h2>Select Your Interests</h2>', 'profile' => true, 'required' => false ) );

	$interests_fields[] = new PMProRH_Field( 
		'interests', 
		'select', 
		array(
			'label' => 'Interests',
			'multiple' => true,
			'profile' => true,
			'required' => false,
			'memberslistcsv' => true,
			'options' => 
				array(
					'' => '',
					'athletics' => 'Athletics',
					'basketball' => 'Basketball',
					'boxing' => 'Boxing',
					'climbing' => 'Climbing',
					'cricket' => 'Cricket',
					'cycling' => 'Cycling',
					'gym' => 'GYM',
					'football' => 'Football',
					'golf' => 'Golf',
					'hockey' => 'Hockey',
					'motocross' => 'Motocross',
					'rugby' => 'Rugby',
					'running' => 'Running',
					'skate' => 'Skate',
					'swimming' => 'Swimming',
					'tennis' => 'Tennis',
					'watersports' => 'Water Sports',
					'wintersports' => 'Winter Sports',
				),
		)
	);

	// Add the fields in the appropriate spot based on the page.
	$checkout_level = $_REQUEST['level'];

	if ( ! empty( $checkout_level ) && in_array( $checkout_level, array(3,7,8) ) ) {
		// Add Interests Fields
		foreach ( $interests_fields as $interests_field ) {
			pmprorh_add_registration_field( 'before_submit_button', $interests_field );
		}

		// Add Gender and Date of Birth Fields
		foreach ( $gender_dob_fields as $gender_dob_field ) {
			pmprorh_add_registration_field( 'before_submit_button', $gender_dob_field );
		}

	} elseif ( ! empty( $checkout_level ) && ( $checkout_level === '5' ) ) {
		// Add Interests Fields
		foreach ( $interests_fields as $interests_field ) {
			pmprorh_add_registration_field( 'after_billing_fields', $interests_field );
		}

		// Add Gender and Date of Birth Fields
		foreach ( $gender_dob_fields as $gender_dob_field ) {
			pmprorh_add_registration_field( 'after_billing_fields', $gender_dob_field );
		}

	} else {
		// Add Interests Fields
		foreach ( $interests_fields as $interests_field ) {
			pmprorh_add_registration_field( 'after_email', $interests_field );
		}

		// Add Gender and Date of Birth Fields
		foreach ( $gender_dob_fields as $gender_dob_field ) {
			pmprorh_add_registration_field( 'after_email', $gender_dob_field );
		}

	}

}
add_action( 'init', 'my_pmpro_rh_custom_fields' );