zend optimizer 安装好了，但是有个警告信息

[root@ip-208-109-24-77 /]# php -v
PHP Warning:  Unknown(): Unable to load dynamic library '/usr/lib/php4/pgsql.so'                      - libpq.so.3: cannot open shared object file: No such file or directory in Unkn                     own on line 0
PHP 4.3.11 (cgi) (built: Jul 29 2005 17:31:06)
Copyright (c) 1997-2004 The PHP Group
Zend Engine v1.3.0, Copyright (c) 1998-2004 Zend Technologies
    with Zend Extension Manager v1.0.10, Copyright (c) 2003-2006, by Zend Techno                     logies
    with Zend Optimizer v3.0.1, Copyright (c) 1998-2006, by Zend Technologies