foreach( array( 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 30, 31, 32 ) as $session_id ) {
    
    $field_id_3 = floatval($session_id .'.3');
    new GW_Inventory( array(
    'form_id'                  => 18,
    'field_id'                 => $field_id_3,
    'stock_qty'                => 25,
    'out_of_stock_message'     => '<div style="border: 1px solid #e6db55; background-color: #FFFFE0; padding: 10px;">' . $field_id_3 . ' Sorry, this session is sold out.</div>',

    'not_enough_stock_message' => 'Sorry, You requested %1$s seats. There are only %2$s seats left.',
    'approved_payments_only'   => false,
    'hide_form'                => false,
    'enable_notifications'     => true
) );
        
}