PHP Configuration - Can't Change Post_Max_Size

This is further to my post yesterday on Max File Size. I was able to set upload_max_filesize to 7900000 and I can therefore upload files up to that size. I would now like to increase that limit, but I am limited by post_max_size which defaults to 8M. I can't seem to change the value of post_max_size. The post_max_size directive is not in my php.ini; however, I tried inserting it into php.ini and setting it to 16000000 and to 16M. I inserted it just before the directive, gpc_order = "GPC". The change is ignored by phpinfo(), that is, phpinfo() still shows post_max_size = 8M. Furthermore, I tried resetting it using ini_set("post_max_size", "16M"), and ini_set("post_max_size", "16000000"), but neither of these had any effect. Any suggestion for how I might reset post_max_size. I'm using PHP 4.0.6. Thanks in advance. Roger