Set which user fields are added as "Extra Fields" to the admin checkout confirmation email. Fields not specified will be removed from the list added to the email.

pmpro-set-admin-email-extra-fields.php

<?php
/**
 * Set which user fields are added as "Extra Fields" to the admin checkout confirmation email.
 *
 * You can add this recipe to your site by creating a custom plugin
 * or using the Code Snippets plugin available for free in the WordPress repository.
 * Read this companion article for step-by-step directions on either method.
 * https://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/
 */

 /**
 * Add user fields to confirmation email.
 */
function my_pmpro_add_user_fields_to_email( $email ) {
	global $wpdb;

	// Set the names of the fields you want to include in the admin email
	$admin_email_fields = array( 'pet_name', 'number_of_pets' );

	//only update admin confirmation emails
	if ( ! empty( $email ) && strpos( $email->template, 'checkout' ) !== false && strpos( $email->template, 'admin' ) !== false && ! empty( $email->data['membership_id'] ) ) {

		//get the user_id from the email
		$user_id = $wpdb->get_var( $wpdb->prepare( "SELECT ID FROM $wpdb->users WHERE user_email = %s LIMIT 1", $email->data['user_email'] ) );

		if ( ! empty( $user_id ) ) {
			//get user fields
			$fields = my_pmpro_get_user_fields_for_user( $user_id );

			// filter fields to only include the ones we want
			$fields = array_filter(
				$fields,
				function( $field ) use ( $admin_email_fields ) {
					return in_array( $field->meta_key, $admin_email_fields );
				}
			);

			// add to bottom of email
			if ( ! empty( $fields ) ) {
				$email->body .= '<p>' . __( 'Extra Fields:', 'paid-memberships-pro' ) . '<br />';
				foreach ( $fields as $field ) {
					if ( ! pmpro_is_field( $field ) ) {
						continue;
					}

					$email->body .= '- ' . $field->label . ': ';

					$value = get_user_meta( $user_id, $field->meta_key, true );
					if ( $field->type == 'file' && is_array( $value ) && ! empty( $value['fullurl'] ) ) {
						$email->body .= $value['fullurl'];
					} elseif ( is_array( $value ) ) {
						$email->body .= implode( ', ', $value );
					} else {
						$email->body .= $value;
					}

					$email->body .= '<br />';
				}
				$email->body .= '</p>';
			} else {
				$email->body .= '<p>' . __( 'No extra fields.', 'paid-memberships-pro' ) . '</p>';
			}
		}
	}

	return $email;
}

function swop_pmpro_add_user_fields_to_email_filters() {
	if ( function_exists( 'my_pmpro_get_user_fields_for_user' ) && function_exists( 'my_pmpro_add_user_fields_to_email' ) ) {
		remove_filter( 'pmpro_email_filter', 'pmpro_add_user_fields_to_email', 10, 2 );
		add_filter( 'pmpro_email_filter', 'my_pmpro_add_user_fields_to_email', 10, 2 );
	}
}
add_action( 'init', 'swop_pmpro_add_user_fields_to_email_filters' );

// get fields for a user's checkout level
function my_pmpro_get_user_fields_for_user( $user_id, $withlocations = false ) {
	global $pmpro_user_fields;

	$user_fields = array();
	if ( ! empty( $pmpro_user_fields ) ) {
		//cycle through groups
		foreach ( $pmpro_user_fields as $where => $fields ) {
			//cycle through fields
			foreach ( $fields as $field ) {
				if ( ! pmpro_is_field( $field ) ) {
					continue;
				}

				if ( ! pmpro_check_field_for_level( $field, 'profile', $user_id ) ) {
					continue;
				}

				if ( $withlocations ) {
					$user_fields[ $where ][] = $field;
				} else {
					$user_fields[] = $field;
				}
			}
		}
	}

	return $user_fields;
}