in the current (CVS) version of PHP3, this alias
is definend in php3/functions/sybase.c

in the current (CVS) version of PHP4, this alias
is definend in php4/ext/mssql/php_mssql.c
and implemented in php4/ext/mssql/php_mssql.c

it is documented in mssql.xml

a japanese translation is available

there is a proto in latest PHP3 source:

bool mssql_close([int link_id]) Close MS-SQL connection

there is a proto in latest PHP4 source:

int mssql_close([int connectionid]) Closes a connection to a MS-SQL server