Someone

<VirtualHost SERER'S-IP:80>
  ServerName username.server.com
  ServerAlias www.username.server.com
  DocumentRoot /var/www/users/username/
  CBandSpeed 2048 20 50
   <Directory /var/www/users/username>
     DirectoryIndex index.html index.htm index.shtml index.php index.php3 index.php4
     Options Indexes +ExecCGI +IncludesNOEXEC +MultiViews +SymLinksIfOwnerMatch
     AllowOverride AuthConfig FileInfo Indexes Limit Options
     php_admin_value max_execution_time 5
     php_admin_value upload_tmp_dir /tmp
     php_admin_value open_basedir /tmp:/var/www/users/username/
   </Directory>
</VirtualHost>