要使用这些 FTP 相关函数，在编译的时候请添加 --enable-ftp 选项。
PHP 5 的 Windows 版本已内建对此扩展的支持。不需要载入额外的扩展来使用这些函数。
从 PHP 7.0.0 开始的 Windows 版本，默认以动态的方式载入该扩展，使用前需要在 php.ini 中开启该扩展。
For some reason folks downvoted the previous entry for this, BUT... indeed, as of PHP 7, to enable this on Windows you have to add the line:
extension=php_ftp.dll
to your php.ini to resolve PHP errors that tell you PHP FTP functions are not defined; the line isn't in there (where, many things are and are just commented out).
On linux, one would enable ftp on their php7 server by uncommenting or adding the line "extension=ftp.so" in their php.ini file (likely at /etc/php/php.ini, unless the user moved it).
If you are using PHP 7 under Windows you have to enable ftp in php.ini with extension=php_ftp.dll.