How can I detect an inaccessible database using PHP PDO?

I am using PHP to create a process that monitors our database and hosts a service page on our website if the database is down.

I am using PDO and Oracle.

I am trying to use a single database connection and query it once a minute, alerting people if there is a problem. However, if the database goes down, the script waits 15 minutes before figuring out what the problem is, so my process, which has to check every minute, looks like this:

06:56:46: SUCCESS -- I take down the database after this success
07:12:48: FAILURE - sent email
07:13:48: FAILURE
...

      

        
        
        
      

    

I want to receive my email immediately, not 15 minutes later. Is there a way to do this while maintaining a persistent connection to the database, or should I create a new one every time I prepare and execute a query?

Here's a snippet of code in case it's helpful:

$last_email_time = null; // the time of the last error email sent
$db_conn = null;
$script_start_time = time();

while(true) {
    $success = false;

    // attempt to create a database connection
    if(!$db_conn) {
        try {
            $db_connection_data = $g_pdo_connection_data['freedom'];
            $db_conn =  new PDO($db_connection_data['string'], $db_connection_data['user'], $db_connection_data['password']);
            $db_conn->setAttribute (PDO::ATTR_ERRMODE, PDO::ERRMODE_EXCEPTION);
            $db_conn->setAttribute (PDO::ATTR_TIMEOUT, 60);
            if(!$db_conn) {
                throw new Exception("Unable to create a database connection");
            }
        } catch(Exception $e) {
            $last_email_time = handle_error($last_email_time, $e->getMessage());
            $db_conn = null;
        }
    }

    // attempt a query
    if($db_conn) {
        try {
            $q = $db_conn->prepare("SELECT 1 FROM DUAL");
            $q->execute();
            $q->closeCursor();
            if(!$q) {
                throw new Exception("Unable to query the database");
            }
            $success = true;
        } catch(Exception $e) {
            $last_email_time = handle_error($last_email_time, $e->getMessage());
        }
    }

    // remove the maintenance page if we were successful, else clear the connection
    if($success) {
        handle_success();
        $last_email_time = null;
    } else {
        $db_conn = null;
    }

    flush();
    if(ob_get_contents() != '') {
        ob_flush();
    }
    sleep(60);
}