My website PHP version changed from what I set.

Symptoms

The website's .htaccess file was changed to a different PHP version and there is no indication why because PHP Manager shows the correct PHP version in both WHM and the user's cPanel account.

Cause 

The issue typically occurs because there are other domains added or subdomains added with the same documentroot but with different PHP versions.

You can search the user's configuration files to get a look at which domains may share a document root and have different PHP versions set:

CONFIG_TEXT: root@server # grep -E '^document|^phpver' /var/cpanel/userdata/cpuser/*
/var/cpanel/userdata/cpuser/domain.tld:documentroot: /home/cpuser/public_html
/var/cpanel/userdata/cpuser/domain.tld:phpversion: ea-php74
/var/cpanel/userdata/cpuser/subdomain.domain.tld:documentroot: /home/cpuser/public_html
/var/cpanel/userdata/cpuser/subdomain.domain.tld:phpversion: ea-php56

Resolution

Access the MultiPHP Manager to ensure that the desired PHP version is selected:

1. Access the server through WHM as the root user or the cPanel account as the cPanel user.
2. In WHM or cPanel, navigate to Home / Software / MultiPHP Manager. 
3. Find the domains that share a document root, and ensure they use the desired PHP version