sub db_open {
my $db = 'test'; my $host = 'localhost';
my $user = 'test'; my $pw = '123456';
my $dsn = "DBI:mysql:database=$db;host=$host";
my $opt = { RaiseError => 1, AutoCommit => 1 };
my $dbh = DBI->connect($dsn, $user, $pw, $opt);
return $dbh;
}