[Solved] Codeigniter: Load Library in a Core Class

Here's the same answer I posted in response to your stackoverflow question.

I'd be interested in this community's thoughts on my answer.

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Extending CI_Log is not going to work if you need to access other libraries. The reason is CI_Log is created long before $CI is created so no "instance" is available for &get_instance() to return.

$this->load doesn't work because $this is not a controller ($this and $CI point to the same object in a controller) and the class load (CI_Loader) hasn't been created yet either.

There might be more than one way around this. Seems to me the least hacked way is to make your logger class utilize CI_Log instead of extend it.

application/libraries/Logger.php

PHP Code:

class Logger
{
    protected $CI;

    public function __construct()
    {
        $this->CI = & get_instance();
        $this->CI->load->library('custom_library');
    }

    public function write_log($level, $msg)
    {
        //do stuff with "custom_library"
         $this->CI->custom_library->some_function();

        //use the built-in logging mechanism, a.k.a. CI_Log
        return log_message($level, $msg);
    }

} 


Your `logger' will need to be loaded in a Controller the same as any other library.

PHP Code:

$this->load->library('logger'); 


A usage example might be something like this

PHP Code:

$this->logger->write_log('error', "This is FUBAR"); 


By the time you call $this->load->library('logger'); the log class has been created and is part of $CI (a.k.a. $this). So this line

PHP Code:

   //use the built-in logging mechanism, a.k.a. CI_Log
    return log_message($level, $msg); 


could be done this way instead

PHP Code:

   //use the built-in logging mechanism, a.k.a. CI_Log
    return $this->CI->log->write_log($level, $msg); 


That would be marginally more efficient since all log_message does is call log->write_log anyway. I don't see any problem doing this instead of using log_message.