มึนๆ กับ Fatal error: Call to a member function result_array() on a non-object

<?php
abstract class Report extends Model 
{
	function __construct()
	{
		parent::Model();

		//Make sure the report is not cached by the browser
		$this->output->set_header("Last-Modified: " . gmdate("D, d M Y H:i:s") . " GMT");
		$this->output->set_header("Cache-Control: no-store, no-cache, must-revalidate");
		$this->output->set_header("Cache-Control: post-check=0, pre-check=0", false);
		$this->output->set_header("Pragma: no-cache");
		
		//Create our temp table to work with the data in our report
		$this->Sale->create_sales_items_temp_table();

		//Create our temp table to work with the data in our report  // jeng add
		$this->Receive->create_receives_items_temp_table(); 		 // jeng add
	}
	
	//Returns the column names used for the report
	public abstract function getDataColumns();
	
	//Returns all the data to be populated into the report
	public abstract function getData(array $inputs);
	
	//Returns key=>value pairing of summary data for the report
	public abstract function getSummaryData(array $inputs);
}
?>

<?php
class Receive extends Model
{
	public function get_info($receive_id)
	{
		$this->db->from('receives');
		$this->db->where('receive_id',$receive_id);
		return $this->db->get();
	}
	
	function exists($receive_id)
	{
		$this->db->from('receives');
		$this->db->where('receive_id',$receive_id);
		$query = $this->db->get();

		return ($query->num_rows()==1);
	}

	function save ($items,$supplier_id,$employee_id,$comment,$payment_type,$receive_id=false)
	{
		if(count($items)==0)
			return -1;

		$receives_data = array(
		'supplier_id'=> $this->Customer->exists($supplier_id) ? $supplier_id : null,
		'employee_id'=>$employee_id,
		'payment_type'=>$payment_type,
		'comment'=>$comment
		);

		//Run these queries as a transaction, we want to make sure we do all or nothing
		$this->db->trans_start();

		$this->db->insert('receives',$receives_data);
		$receive_id = $this->db->insert_id();


		foreach($items as $item_id=>$item)
		{
			$cur_item_info = $this->Item->get_info($item_id);

			$receives_items_data = array
			(
				'receive_id'=>$receive_id,
				'item_id'=>$item_id,
				'quantity_purchased'=>$item['quantity'],
				'discount_percent'=>$item['discount'],
				'item_cost_price' => $cur_item_info->cost_price,
				'item_unit_price'=>$item['price']
			);

			$this->db->insert('receives_items',$receives_items_data);

			//Update stock quantity
			$item_data = array('quantity'=>$cur_item_info->quantity + $item['quantity']);
			$this->Item->save($item_data,$item_id);

			foreach($this->Item_taxes->get_info($item_id) as $row)
			{
				$this->db->insert('receives_items_taxes', array(
					'receive_id' 	=>$receive_id,
					'item_id' 	=>$item_id,
					'name'		=>$row['name'],
					'percent' 	=>$row['percent']
				));
			}
		}
		$this->db->trans_complete();

		return $receive_id;
	}

	function get_receive_items($receive_id)
	{
		$this->db->from('receives_items');
		$this->db->where('receive_id',$receive_id);
		return $this->db->get();
	}

	function get_supplier($receive_id)
	{
		$this->db->from('receives');
		$this->db->where('receive_id',$receive_id);
		return $this->Customer->get_info($this->db->get()->row()->supplier_id);
	}
	
	//We create a temp table that allows us to do easy report/receives queries
	public function create_receives_items_temp_table()
	{
		$this->db->query("CREATE TEMPORARY TABLE ".$this->db->dbprefix('receives_items_temp')." 
		(SELECT date(receive_time) as receive_date, receive_id, comment,payment_type, customer_id, employee_id, item_id, supplier_id, quantity_purchased, item_cost_price, item_unit_price, SUM(percent) as item_tax_percent, 
		discount_percent, (item_unit_price*quantity_purchased-item_unit_price*quantity_purchased*discount_percent/100) as subtotal,
		ROUND((item_unit_price*quantity_purchased-item_unit_price*quantity_purchased*discount_percent/100)*(1+(SUM(percent)/100)),2) as total,
		ROUND((item_unit_price*quantity_purchased-item_unit_price*quantity_purchased*discount_percent/100)*(SUM(percent)/100),2) as tax,
		(item_unit_price*quantity_purchased-item_unit_price*quantity_purchased*discount_percent/100) - (item_cost_price*quantity_purchased) as profit

		FROM ".$this->db->dbprefix('receives_items')."
		INNER JOIN ".$this->db->dbprefix('receives')." USING (receive_id) 
		INNER JOIN ".$this->db->dbprefix('items')." USING (item_id) 
		LEFT OUTER JOIN ".$this->db->dbprefix('suppliers')." ON  ".$this->db->dbprefix('items').'.supplier_id='.$this->db->dbprefix('suppliers').'.person_id'."
		LEFT OUTER JOIN ".$this->db->dbprefix('receives_items_taxes')." USING (receive_id, item_id)
		GROUP BY receive_id, item_id)");
				
		//Update null item_tax_percents to be 0 instead of null
		$this->db->where('item_tax_percent IS NULL');
		$this->db->update('receives_items_temp', array('item_tax_percent' => 0));
		
		//Update null tax to be 0 instead of null
		$this->db->where('tax IS NULL');
		$this->db->update('receives_items_temp', array('tax' => 0));

		//Update null subtotals to be equal to the total as these don't have tax
		$this->db->query('UPDATE '.$this->db->dbprefix('receives_items_temp'). ' SET total=subtotal WHERE total IS NULL');
		
	}
	
}
?>