PDO drivers no value in Windows

学习php编程遇到 

Uncaught exception 'PDOException' with message 'could not find driver'  

或者 

Undefined class constant 'MYSQL_ATTR_INIT_COMMAND'

整两个问题,网上找了很多资料,很多是这样解决的

配置php.ini文件添加extension=php_pdo_mysql.dll，这样就开启pdomysql扩展库 

但是我没有解决问题,问题还是老样子,后来在stackoverflow 找到了问题所在

具体链接http://stackoverflow.com/questions/7086859/pdo-drivers-no-value-in-windows

问题出在了

extension_dir = "ext"

改成绝对路径就可以了

; Directory in which the loadable extensions (modules) reside.
; http://php.net/extension-dir
; extension_dir = "./"
; On windows:
extension_dir = "D:/php-5.4.11-Win32-VC9-x86/ext"

原因

in php.ini and php -m was starting fine and reporting that it loaded pdo_mysql, but when I ran phpinfo.php through apache, the driver was missing.

I fixed it by changing the extension_dir to an absolute path. I'm guessing it got confused when running through Apache and made it relative to something else.　　

我固定它通过改变extension_dir绝对路径。我猜它混淆了运行时通过Apache和相对于别的东西。

转载：http://blog.csdn.net/bao0682/article/details/46827111