Loading Libraries
The core libraries are the class files located in the "libraries" folder. In most cases, to use one of these classes involves initializing it within your controllers using the following function:
$this->load->library('class name');
Where class name is the name of the class you want to invoke. For example, to load the validation class you would do this:
$this->load->library('validation');
Once initialized you can use it as indicated in the user guide page corresponding to each class.
Semantic Relevance
The pattern you will use when calling functions is this:
$this->class->function()
We've placed a high value on semantic relevance in the naming of our classes and functions. Here are some examples of function calls you might use in Code Igniter:
$this->email->send()
$this->input->user_agent()
$this->benchmark->elapsed_time()
$this->db->query()
$this->load->helper()
$this->uri->segment()
$this->lang->line()