[php] wp-admin shows blank page, how to fix it?

I faced the same problem and I tried many things such as trying to login through wp-login.php instead of /wp-admin and adding ob_start() in /wp-admin/index.php (if you hit the url /wp-admin it goes for /wp-admin). It showed login page but entering the username and password shows an error like "cookies are blocked due to unexpected output".

I finally got the solution: it happens because the theme or plugins that you installed are not supported.

How to check and fix:

  • Rename the plugin folder name and theme folder name. If opening /wp-admin and entering a valid username and password the dashboard is shown, then it worked.

  • Revert the folder name of plugin and theme, then activate the themes and plugins one by one, cross-checking with /wp-admin. You will find out the unsupported plugin or theme.