使用未定义常量host -假设'host'paypal类(codeigniter库)中的错误

我使用名为paypal_class的codeigniter库。一切都很好，但是在验证ipn函数时，我得到了这个错误。Use of undefined constant host - assumed 'host'，它必须是邮件没有发送给用户的原因。没有任何东西返回。

我是paypal的新手。所以我希望有一个详细的解决方案。谢谢你！如果你还需要其他信息，请询问。

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错误在这一行:

 $fp = fsockopen($url_parsed[host], "80", $err_num, $err_str, 30);

,

$url_parsed = parse_url($this->paypal_url);

下面是ipn函数:

    function validate_ipn() {
    // parse the paypal URL
    $url_parsed = parse_url($this->paypal_url);
    // generate the post string from the _POST vars aswell as load the
    // _POST vars into an arry so we can play with them from the calling
    // script.
    $post_string = '';
    foreach ($_POST as $field => $value) {
        $this->ipn_data["$field"] = $value;
        $post_string .= $field . '=' . urlencode(stripslashes($value)) . '&';
    }
    $post_string.="cmd=_notify-validate"; // append ipn command
    // open the connection to paypal
    $fp = fsockopen($url_parsed['host'], "80", $err_num, $err_str, 30);
    if (!$fp) {
        // could not open the connection.  If loggin is on, the error message
        // will be in the log.
        $this->last_error = "fsockopen error no. $errnum: $errstr";
        $this->log_ipn_results(false);
        return false;
    } else {
        // Post the data back to paypal
        fputs($fp, "POST $url_parsed[path] HTTP/1.1'r'n");
        fputs($fp, "Host: $url_parsed[host]'r'n");
        fputs($fp, "Content-type: application/x-www-form-urlencoded'r'n");
        fputs($fp, "Content-length: " . strlen($post_string) . "'r'n");
        fputs($fp, "Connection: close'r'n'r'n");
        fputs($fp, $post_string . "'r'n'r'n");
        // loop through the response from the server and append to variable
        while (!feof($fp)) {
            $this->ipn_response .= fgets($fp, 1024);
        }
        fclose($fp); // close connection
    }
    if (preg_match("/VERIFIED/i", $this->ipn_response)) {
        // Valid IPN transaction.
        $this->log_ipn_results(true);
        return true;
    } else {
        // Invalid IPN transaction.  Check the log for details.
        $this->last_error = 'IPN Validation Failed.';
        $this->log_ipn_results(false);
        return false;
    }
}

 $fp = fsockopen($url_parsed[host], "80", $err_num, $err_str, 30);

 $fp = fsockopen($url_parsed['host'], "80", $err_num, $err_str, 30);

$url_parsed = parse_url($this->paypal_url);
var_dump($url_parsed);