[PHP] Newbie Question

[Greg]

I have an app that worked with mySQL, but now I'm trying to make it use
SQL Server. The function that connected to to the mySQL was:
 
mysql_pconnect($db_host, $db_user, $db_pass) or die("Unable to connect
to SQL server");
 
I tried to change it to "sql_pconnect($db_host, $db_user, $db_pass) or
die("Unable to connect to SQL server");" but I get an error that the
function doesn't exist. I'm sure it's something simple, but what's the
php function that will let me connect to the SQL Server?