Error message

• Warning: Cannot modify header information - headers already sent by (output started at /home/sitotours/public_html/includes/common.inc:2797) in drupal_send_headers() (line 1499 of /home/sitotours/public_html/includes/bootstrap.inc).
• ParseError: syntax error, unexpected 'class' (T_CLASS) in _registry_check_code() (line 11 of /home/sitotours/public_html/modules/system/system.mail.inc).