Stock Quote Retreiver Model for CakePHP project

StockQuote.php

<?php 

/**
 * Model that handles the Stock quote. 
 */
class StockQuote extends AppModel {

	/**
	 * update() - main method called by cron jobs and task schedulers to update 
	 * latest stock quote information
	 */
	public function update() {
		$this->_updateStockQuoteCSV();
		$this->_updateStockChartImage();
	}
	
	/**
	 * Deletes any cached services responses for StockQuotes. This is specifically 
	 * for the client application, not involved with any service calls to 3rd 
	 * parties.
	 */
	private function deleteStockQuoteCache(){
		App::import('core', 'Folder');
		$Folder = new Folder();
		$Folder->delete(WWW_ROOT . 'cache/services/day/' . (string)date("Y-m-d") . '.json');		
	}
	  
	/**
	 * Handles calling the third party api, retreives and stores stock quote 
	 * information as well as saves the data to a csv file in the webroot 
	 * directory.
	 */
	public function _updateStockQuoteCSV() {
		$fileName = APP."webroot/assets/quotes.csv";
		$file = fopen($fileName, 'w') or die("Couldn't open file $fileName for writing.");
		$data = file_get_contents('http://download.finance.yahoo.com/d/quotes.csv?s=GOOGA&f=nl1t1cpobb6aa5a2mw&e=.csv'); 
		$parts= preg_split('/,/', $data);
		
		$dateTime = new DateTime("now", new DateTimeZone('America/New_York'));
		$trade_date=date("Y-m-d");
		
		$result=$this->findByTradeDate($trade_date);
		if(isset($result['StockQuote']))
		{
			$this->updateAll(array('StockQuote.raw' => "'".$data."'",'trade_time' => $parts[2], 'value'=> $parts[1],'value_change'=>$parts[3]),    array('StockQuote.trade_date' => $trade_date));						
		}
		else
		{
			$this->create();
			$this->set(array('raw' => $data, 'trade_date' => $trade_date, 'trade_time' => $parts[2], 'value'=> $parts[1],'value_change'=>$parts[3]));
			$this->save();
		}	
	
		fwrite($file, $data);
		fclose($file);
		$this->deleteStockQuoteCache();
	}

	/**
	 * Updates the stock chart image from the 3rd party api. Stores it locally 
	 * on the filesystem for use on the client application.
	 */
	public function _updateStockChartImage() {
		$ch = curl_init ("http://chart.finance.yahoo.com/c/1y/m/GOOG?lang=en-US&region=US"); 
		curl_setopt($ch, CURLOPT_HEADER, 0); 
		curl_setopt($ch, CURLOPT_RETURNTRANSFER, 1); 
		curl_setopt($ch, CURLOPT_BINARYTRANSFER,1); 
		$rawdata=curl_exec ($ch); 
		curl_close($ch);
		
		$fileName = APP."webroot/assets/stock_chart.png";
		$fp = fopen($fileName,'w'); 
		fwrite($fp, $rawdata); 
		fclose($fp);
	}
	
}

?>