Examples of how to change the ticket selector submit button text from 'Register Now' to 'Purchase Tickets' and also how to change the 'View Details' button to

functions.php

<?php //Please do not include the opening PHP tag if you already have one.

function tw_ee_custom_filter_ticket_selector_submit_button_text( $btn_text, $event ) {
  
  return __( 'Purchase Tickets', 'event_espresso' );

}
add_filter( 'FHEE__EE_Ticket_Selector__display_ticket_selector_submit__btn_text', 'tw_ee_custom_filter_ticket_selector_submit_button_text', 10, 2 );

functions2.php

<?php //Please do not include the opening PHP tag if you already have one.

//Another example that uses a custom field within the event.
//Set a ee_custom_register_text custom field with the string you want to replace the default text with on that event as the value.
//If no value has been set default to the standard button text (Register Now).

function tw_ee_custom_filter_ticket_selector_submit_button_text( $btn_text, $event ) {
  
  $ee_custom_register_text = $event->get_post_meta( 'ee_custom_register_text', true );
  
  if ( $ee_custom_register_text ) {
    $btn_text = __( 'Custom Register Text Here', 'event_espresso' );
  }
  
  return $btn_text;
}
add_filter( 'FHEE__EE_Ticket_Selector__display_ticket_selector_submit__btn_text', 'tw_ee_custom_filter_ticket_selector_submit_button_text', 10, 2 );

functions3.php

<?php //Please do not include the opening PHP tag if you already have one.

//Another example that uses a custom field within the event for the 'View Details' text.
//Set a ee_custom_view_details_text custom field with the string you want to replace the default text with on that event as the value.
//If no value has been set default to the standard button text (Register Now).

function tw_ee_custom_filter_ticket_selector_view_details_button_text( $btn_text, $event ) {
  
  $ee_custom_register_text = $event->get_post_meta( 'ee_custom_view_details_text', true );
  
  if ( $ee_custom_register_text ) {
    return $ee_custom_register_text;
  }
  
  return $btn_text;
}
add_filter( 'FHEE__EE_Ticket_Selector__display_view_details_btn__btn_text', 'tw_ee_custom_filter_ticket_selector_view_details_button_text', 10, 2 );