When migrating from our server to our clients server we ran into a strange problem. Basically whenever the user tried to login at /wp-admin. They would be sent into an endless loop. This loop would send the user back to the login page as though nothing happened. After hours of work we finally fixed this error… a long the way I found out that there are any many different issues that may be causing this loop. So here is the way we troubleshooted the problem.
1. Try deleting your browsers cache and cookies. Once this is done restart your computer. If this doesn’t fix the problem then I am sorry.. continue to number 2. If it does work… your welcome and your lucky.
2. Go to your wp-config file and add the following to the top right after <?php add the following:
@define(‘ADMIN_COOKIE_PATH’, ‘/’);
Now try accessing the backend. If that doesn’t work delete the added code.
3. If two did not work try deleting your .htaccess file, if that doesn’t help then restore your .htaccess file.
4. Connect to your database ( via PhpMyAdmin for example) and find the wp_options. Click on it. Then click “check all” and hit the browse button which is between “with selected” and the pencil graphic. Next look for an option name that is “active_plugins”, which is probably located on page 2 by default because it has an option_id of 36. Once you find it click on the pencil located to the left hand side. Copy and delete everything in the text field option_value and replace it with the following code:
a:0:{}
Then hit go. This will deactivate all of the plugins associated with the wordpress site. It will probably make your site look strange temporarily because the plugins are deactivated.
Then try logging in… again… If that doesn’t work paste your code back into the section you just edited and move on to number 5.
5. Give up and just try to re-install wordpress under a fresh directory like “/test”. See if there any errors during the installation. In my case the owner of the server failed to inform us that they don’t keep their php up to date. So we where trying to load a php 5.2 software onto php 5.1…. WHOOOPS… With that piece of information we were able to fix the issue very quickly.
