first transactions

Hello.

I think I need some help on making it clear on how to use transactions
in php in a "correct" way.

Lets consider this code/pseudocode

function dostuff()
{
$db = pg_pconnect...;
pg_query("begin work",$db);
$result = pg_query("select ***",$db);
$result = pg_query("insert ***",$db);

if previous query failed, then rollback and return false
else
{
$result = pg_query("update ***",$db);
$result = pg_query("select ***",$db);
$result = pg_query("insert ***",$db);
$result = pg_query("update ***",$db);
pg_query("commit,$db);
if everything was successfully committed
return true;
else
return false or some other kind of error status to tell what went wrong.
}

} //end function

So the question is: how do I write the pseudocode parts in php?
Any other general suggestions on how to make the function more "fool
proof" is appreciated. :-)