Another "Unable to Login to Admin" Issue

Brand new user here with a completely virgin install of V1.5.0 (via Softaculous for convenience). And yes, I've spent 3 hours scouring these fora but still unable to solve the problem. However, I may have a twist which I did not see covered.

To start, the installation went without error and the "default" storefront seems to operate properly. I can create an account in the storefront, logoff, login in again, and the account info is in there. I can even use the Contact Me email to send a message to the administrator email.

However, going into the admin area and entering the proper username and password I get a blank screen. The db seems ok because it accepts the name/pw and stores a cookie with a session ID in my Firefox. But no error messages; nothing but a blank screen.

However, the twist is the URL of that blank screen is "http://persianriches.com/zencart/zcadmin/login.php?camefrom=index.php" which, along with the cookie, leads me to believe the login was accepted and control sent to index.php. There, something is messed up and it went back to login.

If I click on Forgot Password, it does the same blank screen but with the URL: "http://persianriches.com/zencart/zcadmin/password_forgotten.php?action=update" No email is sent.

No changes have been made to any of the file, including configuration files. The problem occurs in both Firefox and IE. So things like the database, email, cookies, seem to be working ok.

Any suggestions (or questions)? And thanks very much in advance.

Troubleshooting of Blank Page symptoms: https://www.zen-cart.com/tutorials/index.php?article=82

DrByte:

Troubleshooting of Blank Page symptoms: https://www.zen-cart.com/tutorials/index.php?article=82
Hooray! Now we are getting somewhere.

Thanks, Doc, that's one page I never came across. I think because I was concentrating on login blank pages, not blank pages in general.

Anyway, I also was unaware of log files in the cache file. Whodatunk? So now we at least have an error message:

[23-Feb-2012 11:24:31] PHP Fatal error: Call to undefined function: json_encode() in /home/egypt5/public_html/persianriches/zencart/zcadmin/includes/init_includes/init_admin_history.php on line 34

Thank you!!!

UPDATE: I found this thread and thus will check with my host as to the status of PHP (although they show they are running version 5.2.17). Stand by!

UPDATE: I found this thread and thus will check with my host as to the status of PHP (although they show they are running version 5.2.17). Stand by!

JSON is actually an add-on, so the PHP version isn't the issue. Might be that JSON isn't enabled.

Kairho:

UPDATE: I found this thread and thus will check with my host as to the status of PHP (although they show they are running version 5.2.17). Stand by!
Problem solved! Thanks to a quick response by LunarPages Support. In my control panel is a PHP Configuration page and the first item thereon is "The ".php" file extension will be processed by ##########" It just had to be switched from System Default (which is PHP4) to PHP5.

Really simple. Suggestion to install documentarians: mention this!

Thanks again, Doc, for the pointer which would lead to resolution.