How do I check if PHP is connected to a database already?

Question

Basically in pseudo code I\'m looking for something like

if (connected_to_any_database()) {
    // do nothing
}
else {
    mysql_connect(...)
}

Answer 1

before... (I mean somewhere in some other file you're not sure you've included)

$db = mysql_connect()

later...

if (is_resource($db)) {
// connected
} else {
$db = mysql_connect();
}