如果您使用的是Linux，则不应具有DLL文件，而应具有SO文件. 因此，首先，您必须删除/禁用在php.ini中添加的php_mysqli.dll.

If you are on Linux, you shouldn't have DLL files but SO files. So first, you have to remove / disable the php_mysqli.dll you added in php.ini.

为了使用mysqli，您应该:

In order to use mysqli, you should then :

• 为Ubuntu安装软件包:apt-get install php-mysql
• 检查是否已启用(例如，使用phpinfo())
• 如果未启用，请启用模块-在/etc/php/mods-available/文件夹中检查是否有包含extension=mysqli.so的mysqli.ini，然后检查CLI/FPM/Apache/other是否存在指向该文件的符号链接(例如，对于CLI，在/etc/php/cli/conf.d/:20-mysqli.ini -> ../../mods-available/mysqli.ini中)
• 根据您使用的内容重新启动php/apache/nginx

• install the package for Ubuntu : apt-get install php-mysql
• check if it is already enabled (with phpinfo() for example)
• if not enabled, enable the module - check in /etc/php/mods-available/ folder if there is a mysqli.ini, containing extension=mysqli.so, then check for CLI / FPM / Apache / other if there is the symbolic link pointing to this file (for example for CLI, in /etc/php/cli/conf.d/ : 20-mysqli.ini -> ../../mods-available/mysqli.ini)
• restart php / apache / nginx depending what you are using