Normally this file doesn't exist in your account as it uses the sever's master php.ini file (doing phpinfo will soon tell you this) until you crate a custom one for your account.
Some hosts that offer shared hosting don't normally allow custom php.ini files as a security measure (although they rarely allow image scripts on shared anyway) if you happen to be with arvixe they allow this - click here for crating a custom php.ini file.