Pass *only* the event name and last related datetime to PayPal (PayPal Express & PayPal Pro) for the order description. Requires Event Espresso 4.

paypal_event_name_and_last_related_datetime.php

<?php
//* Please do NOT include the opening php tag, except of course if you're starting with a blank file

// event name and date only

add_filter( 'FHEE__EE_Gateway___order_description', 
  'my_custom_order_description_with_date', 10, 3 
);
function my_custom_order_description_with_date( $desc, $gateway, $payment ) {
  $desc = 'Tickets';
  $transaction = $payment->transaction();
  if( $transaction instanceof EEI_Transaction ) {
    $primary_registrant = $transaction->primary_registration();
    if( $primary_registrant instanceof EE_Registration ) {
      $event = $primary_registrant->event_obj();
      if ( $event instanceof EEI_Event ) {
        $desc = $event->name(); 
      }
      $datetime = $primary_registrant->get_latest_related_datetime();
      if ( $datetime instanceof EE_Datetime ) {
        $desc .= ' on ';
        $desc .= $datetime->start_date();
      }
    }
  }
  return $desc;
}

paypal_event_name_venue_and_date.php

<?php
//* Please do NOT include the opening php tag, except of course if you're starting with a blank file

// Event name, venue name, and date 

add_filter( 'FHEE__EE_Gateway___order_description', 
  'my_custom_order_description_with_date', 10, 3 
);
function my_custom_order_description_with_date( $desc, $gateway, $payment ) {
  $desc = 'tickets';
  $transaction = $payment->transaction();
  if( $transaction instanceof EEI_Transaction ) {
    $primary_registrant = $transaction->primary_registration();
    if( $primary_registrant instanceof EE_Registration ) {
      $event = $primary_registrant->event_obj();
      if ( $event instanceof EEI_Event ) {
        $desc = $event->name();
        $venues = $event->venues();
        $venue = reset($venues);
        if ($venue instanceof EE_Venue) {
            $desc .= ' at ';
            $desc .= $venue->name();
        }
      }
      $datetime = $primary_registrant->get_latest_related_datetime();
      if ( $datetime instanceof EE_Datetime ) {
        $desc .= ' on ';
        $desc .= $datetime->start_date();
      }
    }
  }
  return $desc;
}

paypal_order_desc.php

<?php
//* Please do NOT include the opening php tag, except of course if you're starting with a blank file

// event name only

add_filter( 'FHEE__EE_Gateway___order_description', 
  'my_custom_order_description', 10, 3 
);
function my_custom_order_description( $desc, $gateway, $payment ) {
  $desc = 'Tickets';
  $transaction = $payment->transaction();
  if( $transaction instanceof EEI_Transaction ) {
    $primary_registrant = $transaction->primary_registration();
    if( $primary_registrant instanceof EE_Registration ) {
      $event = $primary_registrant->event_obj();
      if ( $event instanceof EEI_Event ) {
        $desc = $event->name(); 
      }
    }
  }
  return $desc;
}