gettext change confirmation message

change_text_example.php

<?php

// Add this code below to your PMPro Customizations plugin - http://www.paidmembershipspro.com/create-a-plugin-for-pmpro-customizations/

function gettext_change_text_example( $translated_text, $text, $domain ) {
	if ( 'paid-memberships-pro' === $domain ) {
		switch ( $text ) {
			case 'You have selected the %s membership level.':
				$translated_text = __( 'You have selected the %s membership level. Thank you for your support.', 'paid-memberships-pro' );
				break;
			case 'Text string to replace here':
				$translated_text = __( 'Your replacement text string here.', 'paid-memberships-pro' );
				break;

			case 'Another text string to replace here':
				$translated_text = __( 'Your replacement text string here', 'paid-memberships-pro' );
				break;
		}
	}
	return $translated_text;
}
add_filter( 'gettext', 'gettext_change_text_example', 20, 3 );