Try creating a phpinfo.php file on the site to see where the php.ini file is being loaded from.
<?php
// Show all information, defaults to INFO_ALL
phpinfo();
?>
Hello, I've run PHP test from PLESK default page and this is what I've got :
PHP Version 5.2.17
System Windows NT ******** 6.1 build 7601
Build Date Jan 6 2011 17:26:08
Configure Command cscript /nologo configure.js "--enable-snapshot-build" "--enable-debug-pack" "--with-snapshot-template=d:\php-sdk\snap_5_2\vc6\x86\template" "--with-php-build=d:\php-sdk\snap_5_2\vc6\x86\php_build" "--with-pdo-oci=D:\php-sdk\oracle\instantclient10\sdk,shared" "--with-oci8=D:\php-sdk\oracle\instantclient10\sdk,shared" "--without-pi3web"
Server API CGI/FastCGI
Virtual Directory Support enabled
Configuration File (php.ini) Path C:\Windows
Loaded Configuration File C:\Program Files (x86)\Parallels\Plesk\Additional\PleskPHP5\php.ini
Scan this dir for additional .ini files (none)
additional .ini files parsed (none)
PHP API 20041225
PHP Extension 20060613
Zend Extension 220060519
Debug Build no
Thread Safety enabled
Zend Memory Manager enabled
IPv6 Support enabled
Registered PHP Streams php, file, data, http, ftp, compress.zlib, https, ftps, zip
Registered Stream Socket Transports tcp, udp, ssl, sslv3, sslv2, tls
Registered Stream Filters convert.iconv.*, string.rot13, string.toupper, string.tolower, string.strip_tags, convert.*, consumed, zlib.*
Configuration
PHP Core
safe_mode Off Off
safe_mode_exec_dir no value no value
safe_mode_gid Off Off
safe_mode_include_dir no value no value
Let me know if you need more info,
Regards
Raf