$conn1 = mysql_connect("xxxxx", "xxx", "xx");
mysql_select_db("xxxxx", $conn1);
$conn2 = mysql_connect("yyyyy", "yyy", "yy");
mysql_select_db("yyyy", $conn2);

$sql = "select ....";
$result = mysql_query($sql, $conn1);
$sql = "up...";
mysql_query($sql, $conn2);