Don't bother disconnecting. The cost of checking $_connected before each query combined with the cost of actually calling $db->disconnectFromDB(); to do the closing will end up being more expensive than just letting PHP close the connection when it is finished with each page.

Don't bother disconnecting. The cost of checking $_connected before each query combined with the cost of actually calling $db->disconnectFromDB(); to do the closing will end up being more expensive than just letting PHP close the connection when it is finished with each page.

Reasoning:

1: If you leave the connection open till the end of the script:

• PHP engine loops through internal array of mysql connections
• PHP engine calls mysql_close() internally for each connection

2: If you close the connection yourself:

• You have to check the value of $_connected for every single query. This means PHP has to check that the variable $_connected A) exists B) is a boolean and C) is true/false.
• You have to call your 'disconnect' function, and function calls are one of the more expensive operations in PHP. PHP has to check that your function A) exists, B) is not private/protected and C) that you provided enough arguments to your function. It also has to create a copy of the $connection variable in the new local scope.
• Then your 'disconnect' function will call mysql_close() which means PHP A) checks that mysql_close() exists and B) that you have provided all needed arguments to mysql_close() and C) that they are the correct type (mysql resource).

I might not be 100% correct here but I believe the odds are in my favour.