Since Plesk 10.4, it is possible to customize PHP settings on per-domain basis from control panel interface. See KB article #113861 for instructions.
In Plesk 10.3.x and earlier, separate PHP configuration parameters can be managed on a per-directory basis by adjusting Windows Registry as recommended in PHP Manual.
For example, if it is required to disable
safe_mode for virtual host's httpdocs directory, registry key "
HKLM\SOFTWARE\Wow6432Node\PHP\Per Directory Values\C\Inetpub\vhosts\domain.com\httpdocs" (replace
C\Inetpub\vhosts\domain.com\httpdocs with actual path to the directory) should be created and new REG_SZ value with name
safe_mode and value
Off created in this key.
If PHP is running as ISAPI on domain, then site's IIS application pool must be restarted to apply the changes.