example.php

<?php

// Example of hot to change the 'Proceed to Finalize Registration' text depending on the cart total.
add_filter ( 'FHEE__EE_SPCO_Reg_Step__set_submit_button_text___submit_button_text', 'ee_finalize_registration_button', 10, 2 );
function ee_finalize_registration_button( $submit_button_text, EE_Checkout $checkout ) {
	if ( ! $checkout instanceof EE_Checkout || ! $checkout->current_step instanceof EE_SPCO_Reg_Step || ! $checkout->next_step instanceof EE_SPCO_Reg_Step ) {
 		return $submit_button_text;
 	}
 	if ( $checkout->next_step->slug() == 'finalize_registration' ) {
		if ( $checkout->cart instanceof EE_Cart && $checkout->cart->get_cart_grand_total() != 0 ) {
  			$submit_button_text = 'PAID';
		} else {
			// The total for the cart is 0, so the tickets currently in the cart are all free.
			$submit_button_text = 'FREE';
		}
 	}
 	return $submit_button_text;
}