sessionClose

Example D-6. The sessionClose handler

// This function is executed on shutdown of the session.
// Always returns true.
function sessionClose($sess_id)
{
    return true;
}

sessionDestroy

When session_destroy( ) is called, the sessionDestroy( ) handler shown in Example D-7 is called. This function deletes the row identified by the $sess_id argument from the table that holds the session variables.

Example D-7. The sessionDestroy handler

// This is called whenever the session_destroy(  )
// function call is made. Returns true if the session
// has successfully been deleted.
function sessionDestroy($sess_id)
{
  global $connection;
  global $session_table;
  $delete_query =
    "DELETE FROM $session_table
      WHERE session_id = '$sess_id'";
  if (!($result = @ mysql_query($delete_query,
                                $connection)))
     showerror(  );
  return true;
}

Garbage collection

The last handler to be defined is the garbage collection function. Example D-8 shows the implementation of sessionGC( ), which queries for all session rows that have been dormant for $max_lifetime seconds. PHP passes the value set in the session.gc_maxlifetime parameter of the php.ini file. The time a session has been dormant is calculated by subtracting the last update time-held in the session row-from the current time.

Example D-8. Garbage collection handler

// This function is called on a session's start up with
// the probability specified in session.gc_probability.
// Performs garbage collection by removing all sessions
// that haven't been updated in the last $max_lifetime
// seconds as set in session.gc_maxlifetime.
// Returns true if the DELETE query succeeded.
function sessionGC($max_lifetime)
{
  global $connection;
  global $session_table;
  $time_stamp = getMicroTime(  );
  $delete_query =
    "DELETE FROM $session_table
      WHERE last_accessed < ($time_stamp - $max_lifetime)";
  if (!($result = @ mysql_query($delete_query,
                                $connection)))
     showerror(  );
  return true;
}