Executes a CURL request to bitcoin ticker APIs, gets the JSON reply, formats it as an output string

Bitcoin.ticker.php

<?PHP
	//Executes a CURL request to bitcoin ticket APIs, gets the JSON reply

	//Todo: API JSON error detection, more sites
	
	$bitcoin_sites = array(
		array(
			'name' => 'Mt.Gox [Dead]',
			'coins' => array(
				array(
					'coin' => 'BTC',
					'api_url' => 'https://data.mtgox.com/api/2/BTCUSD/money/ticker',
					'json_index' => array('data', 'last', 'value'),
					'json_reply' => '',
					'last_price' => '',
					'price_unit' => '$',
					'curl' => null,
				),
			),
		),
		array(
			'name' => 'BitStamp',
			'coins' => array(
				array(
					'coin' => 'BTC',
					'api_url' => 'https://www.bitstamp.net/api/ticker/',
					'json_index' => array('last'),
					'json_reply' => '',
					'last_price' => '',
					'price_unit' => '$',
					'curl' => null,
				),
			),
		),
		array(
			'name' => 'BTC-e',
			'coins' => array(
				array(
					'coin' => 'BTC',
					'api_url' => 'https://btc-e.com/api/2/btc_usd/ticker',
					'json_index' => array('ticker', 'last'),
					'json_reply' => '',
					'last_price' => '',
					'price_unit' => '$',
					'curl' => null,
				),
				array(
					'coin' => 'LTC',
					'api_url' => 'https://btc-e.com/api/2/ltc_usd/ticker',
					'json_index' => array('ticker', 'last'),
					'json_reply' => '',
					'last_price' => '',
					'price_unit' => '$',
					'curl' => null,
				),
				array(
					'coin' => 'NMC',
					'api_url' => 'https://btc-e.com/api/2/nmc_usd/ticker',
					'json_index' => array('ticker', 'last'),
					'json_reply' => '',
					'last_price' => '',
					'price_unit' => '$',
					'curl' => null,
				),
				array(
					'coin' => 'FTC',
					'api_url' => 'https://btc-e.com/api/2/ftc_btc/ticker',
					'json_index' => array('ticker', 'last'),
					'json_reply' => '',
					'last_price' => '',
					'price_unit' => 'B',
					'curl' => null,
				),
			),
		),
	);

	$multi_curl = curl_multi_init();

	foreach ($bitcoin_sites as &$site) {
		foreach ($site['coins'] as &$coin) {
			$coin['curl'] = curl_init();
			curl_setopt($coin['curl'], CURLOPT_RETURNTRANSFER, true);
			curl_setopt($coin['curl'], CURLOPT_HEADER, 0);
			curl_setopt($coin['curl'], CURLOPT_TIMEOUT, 10); //Seconds
			curl_setopt($coin['curl'], CURLOPT_URL, $coin['api_url']);
			curl_multi_add_handle($multi_curl, $coin['curl']);
		}
	}

	//Execute each curl concurrently for speed
	do {
	    $mrc = curl_multi_exec($multi_curl, $active);
	} while ($mrc == CURLM_CALL_MULTI_PERFORM);

	while ($active && $mrc == CURLM_OK) {
	    if (curl_multi_select($multi_curl) != -1) {
	        do {
	            $mrc = curl_multi_exec($multi_curl, $active);
	        } while ($mrc == CURLM_CALL_MULTI_PERFORM);
	    }
	}

	$output_string = 'Last Prices:';

	foreach ($bitcoin_sites as &$site) {

		$output_string .= ' '.$site['name'].' ';

		foreach ($site['coins'] as &$coin) {

			$coin['json_reply'] = curl_multi_getcontent($coin['curl']);

			curl_multi_remove_handle($multi_curl, $coin['curl']);

			$coin['last_price'] = json_decode($coin['json_reply'], true); //Return as array

			//Since each site stores their last price differently, we implement a workaround:
			//We store the json hierarchy to our target data, 
			//in order, then iterate through them one level at a time
			foreach($coin['json_index'] as $subarray) {
				$coin['last_price'] = $coin['last_price'][$subarray];
			}

			if ($coin['price_unit'] == '$') {
				$coin['last_price'] = number_format($coin['last_price'], 2);
			}

			$output_string .= '['.$coin['coin'].'] ';

			//If price is 0 or null, an error or timeout probably occured
			if ($coin['last_price'] == 0) {
				$output_string .= 'Err. ';
			} else {
				$output_string .= $coin['price_unit'].$coin['last_price'].' ';
			}
		}

		$output_string .= '|';
	}

	$output_string = rtrim($output_string, '|'); //remove trailing pipe

	curl_multi_close($multi_curl);

	//Add ?anything to the url to get the debug view
	if(!empty($_GET)) { 
		foreach ($bitcoin_sites as &$site) { 
			foreach ($site['coins'] as &$coin) {
				$coin['curl_debug'] = curl_getinfo($coin['curl']); //Dump the curl handlers

				echo var_dump($coin['curl_debug']);
			}
		} 

	} else { 
		echo $output_string; 
	}

?>