Question

How can I check if a db-connection is open in PHP?

How can I get a reference to this connection?

How can I determine if it is MySQL, Postgres or something else?

Answer 1

Ideally you would know the variable the connection is saved into. Without this it becomes a hassle to find it. It means you would have to loop through every variable and test each one, but doing this for any reason can be a pain because it wont find variables outside of the current scope. You can loop the current variables using:

foreach(get_defined_vars() as $x){
    // Code
}

To check if a variable is a valid connection you can use the below code, it should return an integer:

if(mysql_thread_id($connection){
    // Connection exists
}

Once you know its a connection you can use the following to return the type of connection, eg, mysql.

echo get_resource_type($connection);