BTC-e Trading Bot Written in PHP

error_reporting(E_ALL ^ E_DEPRECATED);
ini_set('display_errors',1);
 
//mysql connection to the DB we created above. Note that mysql_* extension is deprecated as of today and will soon be removed
mysql_connect('localhost','user','password');
mysql_select_db('dbname');
 
// we will loop through market depth starting from the cheapest, until we reach the amount we can buy 5 BTC's for
define('BTC_AMOUNT_TO_REFLECT_PRICE',5);
// we will loop through market depth starting from the cheapest, until we reach the amount we can buy 1000 USD's for
define('USD_AMOUNT_TO_REFLECT_PRICE',1000);
 
//when our indicator (see below the code) increases more than 500, we should sell
//when our indicator (see below the code) goes below  -500, we should buy
define('SELL_THRESHOLD',500);
define('BUY_THRESHOLD',-500);
 
date_default_timezone_set('Europe/Berlin');
 
//our API keys
define('API_KEY','XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXX-XXXXXXXX');
define('API_SECRET','XXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXXX');

$depth = json_decode(file_get_contents('https://btc-e.com/api/2/btc_usd/depth'));

function btce_query($method, array $req = array()) {
    try {
        // API settings
        $key = API_KEY; // your API-key
        $secret = API_SECRET; // your Secret-key
 
        $req['method'] = $method;
        $mt = explode(' ', microtime());
        $req['nonce'] = $mt[1];
 
        // generate the POST data string
        $post_data = http_build_query($req, '', '&');
 
        $sign = hash_hmac('sha512', $post_data, $secret);
 
        // generate the extra headers
        $headers = array(
                        'Sign: '.$sign,
                        'Key: '.$key,
        );
 
        // our curl handle (initialize if required)
        static $ch = null;
        if (is_null($ch)) {
                $ch = curl_init();
                curl_setopt($ch, CURLOPT_RETURNTRANSFER, true);
                curl_setopt($ch, CURLOPT_USERAGENT, 'Mozilla/4.0 (compatible; BTCE PHP client; '.php_uname('s').'; PHP/'.phpversion().')');
        }
        curl_setopt($ch, CURLOPT_URL, 'https://btc-e.com/tapi/');
        curl_setopt($ch, CURLOPT_POSTFIELDS, $post_data);
        curl_setopt($ch, CURLOPT_HTTPHEADER, $headers);
        curl_setopt($ch, CURLOPT_SSL_VERIFYPEER, FALSE);
 
        // run the query
        $res = curl_exec($ch);
        if ($res === false) throw new Exception('Could not get reply: '.curl_error($ch));
        $dec = json_decode($res, true);
        if (!$dec) throw new Exception('Invalid data received, please make sure connection is working and requested API exists');
        return $dec;
    } catch(Exception $e) {echo 'got Exception: ' . $e->getMessage() . PHP_EOL;}
}

while(1) {
    //get current market depth
    $depth = json_decode(file_get_contents('https://btc-e.com/api/2/btc_usd/depth'));
 
    $sum_usd = $sum_btc = $usd = $btc = $current_rate_btc = $current_rate_usd = 0;
    // loop through all bids (sorted ascending) until we reach BTC_AMOUNT_TO_REFLECT_PRICE  constant
    if(is_array($depth->bids) && is_array($depth->asks)) {
        foreach($depth->bids as $bid) {
            $btc += $bid[1];
            if($btc >= BTC_AMOUNT_TO_REFLECT_PRICE && !$current_rate_btc) {
                $current_rate_btc = $bid[0];
            }
            $sum_usd += $bid[0]  * $bid[1];
        }
 
        $bids_avg = $sum_usd / count($depth->bids);
    // loop through all asks (sorted ascending) until we reach USD_AMOUNT_TO_REFLECT_PRICE constant
        foreach($depth->asks as $ask) {
            $usd += $ask[0];
            if($usd >= USD_AMOUNT_TO_REFLECT_PRICE && !$current_rate_usd) {
                $current_rate_usd = $ask[0];
            }
            $sum_btc += $ask[0]  * $ask[1];
        }
 
        $asks_avg = $sum_btc / count($depth->asks);
 
        ////////////////////////////////////////////
        // get last 3 previous records (last 15 seconds) from depth_log table to get our indicator - whether to buy or sell
        $res = mysql_query('SELECT * FROM `depth_log` ORDER BY `id` desc limit 3');
 
        $flag_buy = $flag_sell = true;
        while(($row = mysql_fetch_assoc($res)) !== false) {
            if($row['abs'] > BUY_THRESHOLD) {
                $flag_buy = false;
            }
            if($row['abs']  5) {
                $amount_btc = (0.9975 * $usd_balance ) / $current_rate_usd;
                $result = btce_query('Trade',array('pair' => 'btc_usd', 'type' => 'buy', 'rate' => round($current_rate_usd,2), 'amount' => round($amount_btc,6)));
 
                mysql_query(sprintf('INSERT INTO `transactions`(`type`,`amount_btc`,`amount_usd`,`rate`) VALUES("buy",%.5f,0,%.5f)',mysql_real_escape_string($amount_btc),$current_rate_usd));
            }
 
            // if flag_sell AND we have BTC's, then sell
            if($flag_sell && $btc_balance > 0.02) {
                $amount_btc = (0.9975 * $btc_balance);
                $result = btce_query('Trade',array('pair' => 'btc_usd', 'type' => 'sell', 'rate' => round($current_rate_btc,2), 'amount' => round($amount_btc,6)));
 
                mysql_query(sprintf('INSERT INTO `transactions`(`type`,`amount_btc`,`amount_usd`,`rate`) VALUES("sell",%.5f,0,%.5f)',mysql_real_escape_string($amount_btc),$current_rate_btc));
            }
        }
    }
    // sleep for 5 seconds
    sleep(5);
}