为了使这些函数可用，你必须以支持mysqli扩展的方式编译PHP。
Note:
mysqli扩展被设计用于配合Mysql 4.1.13或更新的服务端版本（或者5.0.7或更新）工作。对于此前的数据库服务端版本， 请参阅MySQL扩展文档。
integraljohn at gmail dot com (2012-03-07 19:36:30)
I've just spent some time battling the "fatal error call to undefined function mysql_connect()" message, and as it wasn't clear to me, I thought it may help to say:
php_mysqli does not replace the php_mysql library. It only extends it. You need the php_mysql library !
dennylin93 at cnmc32 dot hs dot ntnu dot edu dot tw (2009-10-13 07:16:50)
The required extensions will be pulled in automatically on FreeBSD, unless you manually remove them after installation.
tommyhp2 (2009-01-19 18:03:41)
If you're building this on FreeBSD, make sure that you have SPL and SimpleXML in the extensions.ini.