Window 7，PHP，无法加载动态库'C：\ PHP \ ext \ php_oci8.dll'

I installed PHP in window 7, running simple PHP without issue. when I want to connect oracle db 11g XE, using $conn = oci_connect ($user, $pawd, 'localhost/XE'); I get the following errors:

Unable to load dynamic library 'C:\PHP\ext\php_oci8.dll' ...
Unable to load dynamic library 'C:\PHP\ext\php_oci8_11g.dll' ...
PHP Fatal error: Call to undefined function oci_connect (..);

I checked that C:\PHP\ext\php_oci8.dll is there and I changed the following in php.ini file.

extension_dir = "C:\PHP\exe";
extension=php_bz2.dll;
extension=php_curl.dll;
extension=php_oci8.dll;
extension=php_oci8_11g.dll;

what is the issue behind this?

try to copy the files orannzsbb11.dll , oci.dll and oraociei11.dll to c:\windows\system32