ERROR:could not find driver problem occurs when using PDO to operate database in PHP

I have no problem using the built-in MySQL function and mysqli class to operate the database, and I removed the semicolon in front of extension=php_pdo.dll and extension=php_pdo_sqlite.dll in the configuration file (I use AppServ, and there are only the above in the configuration file Two statements have PDO).
Why does "ERROR: could not find driver" still appear? In this case, it prompts you that the pdo driver is not found. Check as follows

1 Whether the file extension=php_pdo.dll exists
2 Open php.ini under Windows, search extension_dir = "address", and check whether there is a folder at this address
3 Check whether the above file is included in the folder
4 Create a new php page, enter preview, check whether the extension has been turned on and try adding a few

extension=php_pdo_mysql.dll
extension=php_pdo_pgsql.dll
extension =php_pdo_mssql.dll
extension=php_pdo_odbc.dll
extension=php_pdo_firebird.dll
It may be because the php_pdo_mysql.dll extension is not added.