<?php
class Projects_model extends Model
{

	private $_tbl = 'projects';

        .......

        // This works for my regular update
	public function updateProject( $id, $project )
	{
		$this->db->where( 'id', $id );
		$this->db->update( $this->_tbl, $project );
	}

        // Entry point
	public function addMainFileUrls()
	{
		$inputs = $this->cleanMainFileInputs();
		$id     = array_shift( $inputs );
		$this->updateProject( $id, $inputs );
	}

        // Cleans up posted info before passing back to addMainFileUrls
	private function cleanMainFileInputs()
	{
		$inputs = array( 'project_id' => 'id',
						 'plans_file' => 'plans_url',
   						 'specs_file' => 'specs_url' );

		$cleanUrls = array();
		foreach ($inputs as $key => $newKey) {
			$cleanUrls[$newKey] = $this->input->post($key);
		}
		return $cleanUrls;
	}
}




<?php

class Projects extends Controller {

        ......

	public function files()
	{
		$this->projects->addMainFileUrls();
		redirect('/projects');
	}


        ......

}

------------------------------------------------------

var_dump of info going to Projects_model::updateProject()

var_dump of $id = string(1) "2"

var_dump of $inputs = array(2) {
  ["plans_url"]=>
  string(10) "A-3.07.pdf"
  ["specs_url"]=>
  string(10) "A-4.04.pdf"
}

-----------------------------------------------------

Updated row in the database:

plans_url = A-3.07.pdf
specs_url = 0