In this blog I w,ill explain you how we can fix PhpMyAdmin secret passphrase error in simple steps.

Fix PhpMyAdmin secret passphrase (blowfish_secret) Issue
If you manually install PhpMyAdmin on your server then go to the PHPMyAdmin directory.
You can rename config.sample.inc.php to config.inc.php. Open this file in your editor.
Now you need to add 32 char in $cfg['blowfish_secret']

Save your file and refresh your PhpMyAdmin page in browser. Now there is no warning on the screen.