Trying to access PHPMyAdmin from cPanel results in errors or the redirection never completes.

Symptoms

When accessing PHPMyAdmin from the cPanel Interface, the following or similar error is presented:

warn [cpanel] Encountered error in Cgi::phpmyadminlink: Cgi::phpmyadminlink failed: (XID cmbzej) The request failed. (Error ID cmbzej) at /usr/local/cpanel/Cpanel/EventHandler.pm line 47.

If no error is presented, a redirection loop will occur, and the browser refreshes, but the PHPMyAdmin interface is not loaded. 

Description 

PHPMyAdmin and MySQL require access to the temporary filesystem, usually just "/tmp." The proper permission and ownership scheme would need to be configured.

For example, the following permission scheme of 775 is not correct:

stat /tmp/
  File: `/tmp/'
  Size: 135168    	Blocks: 272        IO Block: 4096   directory
Device: fd01h/64769d	Inode: 3145752     Links: 381
Access: (0755/drwxr-xr-x)  Uid: (    0/    root)   Gid: (    0/    root)
Access: 2021-03-03 15:27:05.105732707 +0200
Modify: 2021-03-03 15:25:41.563348386 +0200
Change: 2021-03-03 15:25:41.563348386 +0200

Workaround

The correct permission scheme should be 1777, which looks like the following:

stat /tmp/
File: `/tmp/'
Size: 135168 Blocks: 272 IO Block: 4096 directory
Device: fd01h/64769d Inode: 3145752 Links: 381
Access: (1777/drwxrwxrwt) Uid: ( 0/ root) Gid: ( 0/ root)
Access: 2021-03-03 15:40:20.288127565 +0200
Modify: 2021-03-03 15:40:48.874069765 +0200
Change: 2021-03-03 15:40:48.874069765 +0200

The 1777 permission scheme allows for processes running under a specific user to create/modify/delete files while keeping ownership of the created files. 

The 1775 permission scheme can be set by executing the following command as root:

chmod 1777 /tmp