This method simply returns an associative array of the results of query. Its most common use (at least by me) is for result sets that return two columns with the first being unique (or at least supposedly uniqe).
<php
$users = $db->getAssoc("SELECT username, password FROM users");
?>
This could return something like this:
<php
Array
(
[richardh] => yuvuvfvjh,
[joseph] => dreamcoat,
[bob] => dole
)
?>
The second argument (true or false) can used to force the value to be an array, like so:
<php
Array
(
[root] => Array
(
[0] =>
)
[richard] => Array
(
[0] =>
)
[admin] => Array
(
[0] =>
)
[morley] => Array
(
[0] => 262ae87865ac335c
)
)
?>
The third argument isn't used. Whilst the fourth is used to "group" the resulting rows. This means that if you end up with 5 rows all with the same first column, it will be an array of the other values associated with that first column.