调用未定义的函数_curl（）[关闭]

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$uid = mysql_real_escape_string($_SESSION['username']);
$url = "https://blockchain.info/merchant/$guid/new_address?password=$main_password&second_password=$second_password&label=$uid";
if (isset($_POST['amount'])){
    $_SESSION['USD_amount'] = $_POST['amount'];
    $_SESSION['BTC_amount'] = number_format($_SESSION['USD_amount']/$rate, 8, '.', '');
    $temp = _curl($url, '', '');
    $_SESSION['BTC_Address'] = get_string_between($temp, 'address":"', '"');    
}

I have curl the latest version installed but it doesn't seem to fix the problem.

Any suggestion ?

Curl is initiated with, for example:

$ch = curl_init($url);

there's no function called _curl()