I had to install the Zend Optimizer on my server the other day; I have a Plesk dedicated server with GoDaddy, which uses IonCube (I think for Plesk itself). Anyway, I came across some problems which I imagine are pretty common, so here are the solutions.
Getting the IonCube error?
The Loader must appear as the first entry in the php.ini file in Unknown on line 0
I created a “zend.ini” file with the Zend lines from php.ini in there and placed it in /etc/php.d.
That fixed this error. Then I had a new error, “Fatal error: Unable to read X bytes in file.php on line 0”, which I found the answer to here.
So upload the files in binary. Now I have Plesk + ionCube + Zend Optimizer all installed together 😀