By default, Parallels Plesk Panel sets PHP to "safe mode" during installation. To take PHP out of "safe mode," you need to remote connect to your dedicated server and modify the server's PHP initialization file.
safe_mode = onto
safe_mode = off.
Once you have edited the file, you need to restart your Web server. You can restart your Web server using Parallels Plesk Panel by selecting stop/start under the Server > Service Management section.