All fields should be treated as read-only unless explicitly stated otherwise.
The driver must set this during SKEL_handle_preparer().
This item is for use by the driver; the intended usage is to store a pointer (during SKEL_handle_factory()) to whatever instance data is required to maintain a connection to the database.
This is set by PDO after the statement has been executed for the first time. Your driver can inspect this value to determine if it can skip one-time actions as an optimization.
Discussed in more detail in Fleshing out your skeleton.
Your driver is responsible for setting this field to the number of columns available in a result set. This is usually set during SKEL_stmt_execute() but with some database implementations, the column count may not be available until SKEL_stmt_fetch() has been called at least once. Drivers that implement SKEL_stmt_next_rowset() should update the column count when a new rowset is available.
PDO will allocate this field based on the value that you set for the column count. You are responsible for populating each column during SKEL_stmt_describe(). You must set the precision , maxlen , name , namelen and param_type members for each column. The name is expected to be allocated using emalloc(); PDO will call efree() at the appropriate time.