Common Functions
CodeIgniter uses a few functions for its operation that are globally defined, and are available to you at any point. These do not require loading any libraries or helpers.
is_really_writable('path/to/file')
is_writable() returns TRUE on Windows servers when you really can't write to the file as the OS reports to PHP as FALSE only if the read-only attribute is marked. This function determines if a file is actually writable by attempting to write to it first. Generally only recommended on platforms where this information may be unreliable.
if (is_really_writable('file.txt'))
{
echo "I could write to this if I wanted to";
}
else
{
echo "File is not writable";
}
config_item('item_key')
The Config library is the preferred way of accessing configuration information, however config_item() can be used to retrieve single keys. See Config library documentation for more information.
show_error('message'), show_404('page'), log_message('level', 'message')
These are each outlined on the Error Handling page.