This is subtle… I was writing some “reconnect” logic for a DB Class to catch and handle MySQL error code 2006, Server Gone Away. After a solid 5 hours of wasted time I traced the poor logic on my part back to the mysql_connect() function. I was thrown off track at first when the code was hung up on a mysql_select_db() function. Turns out that mysql_connect(), if called twice in an execution series with the same parameters, will take the old link and return that! What The French. So, yes, I read the manual and a fourth param (boolean) can be passed into the function to say I want a NEW connection.
The fourth param is called new_link, and the excerpt from php.net is as follows:
If a second call is made to mysql_connect() with the same arguments, no new link will be established, but instead, the link identifier of the already opened link will be returned. The new_link parameter modifies this behavior and makes mysql_connect() always open a new link, even if mysql_connect() was called before with the same parameters. In SQL safe mode, this parameter is ignored.
Good to know. Better to remember. Necessary to understand. Fail on my part.