I am wondering, on a practical level : what is a database connection? What does it represent for PHP/Java/Ruby/etc to have an opened connection for instance? What about the MySQL deamon? Does it materialize in some way?
From PHP side, I can guess it is an object like any other. I can imagine a similar concept from MySQL's point of view. But is there an "in between" handled by one or both sides that actually materializes the connection in some way?
My apologies if the question sounds very vague. I am so used to speak of PDO "database connections", I realize now that I am not sure at all what that is. I understand what it does, but how it does it just seems very foggy.
Many thanks for every clarification of this concept. Pointing me towards a good reading is considered a valid explanation :D
