Why are error message paths “cut off”?

Suddenly all my WordPress websites quit working again. I am getting the following error. In the past it was because files were missing. However, the error message is truncating the path to the full “require file” it needs.

require_once(‘C:\\Domains\\web-…’)
It says web-…

Full error message–>

[10-Jun-2022 21:32:20 UTC] PHP Fatal error:  Uncaught Error: Call to undefined function mysql_connect() in C:\Domains\web-hosters.com\wwwroot\wp-includes\wp-db.php:1685
Stack trace:
#0 C:\Domains\web-hosters.com\wwwroot\wp-includes\wp-db.php(632): wpdb->db_connect()
#1 C:\Domains\web-hosters.com\wwwroot\wp-includes\load.php(558): wpdb->__construct()
#2 C:\Domains\web-hosters.com\wwwroot\wp-settings.php(124): require_wp_db()
#3 C:\Domains\web-hosters.com\wwwroot\wp-config.php(88): require_once('C:\\Domains\\web-...')
#4 C:\Domains\web-hosters.com\wwwroot\wp-load.php(50): require_once('C:\\Domains\\web-...')
#5 C:\Domains\web-hosters.com\wwwroot\wp-blog-header.php(13): require_once('C:\\Domains\\web-...')
#6 C:\Domains\web-hosters.com\wwwroot\index.php(17): require('C:\\Domains\\web-...')
#7 {main}
  thrown in C:\Domains\web-hosters.com\wwwroot\wp-includes\wp-db.php on line 1685