Virtualhost configuration sometimes change

[Ianta]

When i create a new account, in the httpd.conf on virtualhost configuration sometimes the ServerName is www.domainname.it and Alias domainname.it and sometimes the ServerName is domainname.it and Alias www.domainname.it.

In wich case this configuration change? How can know when the servername is with or without www? This is a little difference, but in php the $_SERVER['SERVER_NAME'] change!

Can someone help me please?

Thank's.

[DigitalN]

When the ServerName is www.domainname.it it usually means the account was added in whm using www.domainname.it rather than domainname.it

[Ianta]

When i create a new account, i use alway domainname.it format