What are the disadvantages of using persistent connection in PDO

Question

In PDO, a connection can be made persistent using the PDO::ATTR_PERSISTENT attribute. According to the php manual -

Persistent connectio

Answer 1

I was just wondering whether a partial solution would be to have a pool of use-once connections. You could spend time creating a connection pool when the system is at low usage, up to a limit, hand them out and kill them when either they've completed or timed out. In the background you're creating new connections as they're being taken. At worst case this should only be as slow as creating the connection without the pool, assuming that establishing the link is the limiting factor?