What are these variables and where are they documented?

See the php sprintf and printf functions. They are tokens that get data from a function or variable separated by commas at the end of the call.

$variable="sprintf";
printf( 'Hey dude check out the %s php function', $variable );

Hata!: SQLSTATE[HY000] [1045] Access denied for user 'divattrend_liink'@'localhost' (using password: YES)