当我尝试使用phpmailer发送电子邮件时，我的代码的结果是致命错误：require（）[function.require]：无法打开所需的“../vendor/autoload.php”（include_path ='.; C：\php\pear'）。我的问题是什么？

<?php
/**
 * This example shows making an SMTP connection with authentication.
 */

//Import the PHPMailer class into the global namespace
use PHPMailer\PHPMailer\PHPMailer;

//SMTP needs accurate times, and the PHP time zone MUST be set
//This should be done in your php.ini, but this is how to do it if you don't have access to that
date_default_timezone_set('Etc/UTC');

require '../vendor/autoload.php';

//Create a new PHPMailer instance
$mail = new PHPMailer;
//Tell PHPMailer to use SMTP
$mail->isSMTP();
//Enable SMTP debugging
// 0 = off (for production use)
// 1 = client messages
// 2 = client and server messages
$mail->SMTPDebug = 2;
//Set the hostname of the mail server
$mail->Host = 'mail.mehregantamin.ir';
//Set the SMTP port number - likely to be 25, 465 or 587
$mail->Port = 25;
//Whether to use SMTP authentication
$mail->SMTPAuth = true;
//Username to use for SMTP authentication
$mail->Username = 'ali@mehregantamin.ir';
//Password to use for SMTP authentication
$mail->Password = '*****';
//Set who the message is to be sent from
$mail->setFrom('ali@mehregantamin.ir', 'First Last');
//Set an alternative reply-to address
$mail->addReplyTo('replyto@example.com', 'First Last');
//Set who the message is to be sent to
$mail->addAddress('vampire.programmer@gmail.com', 'John Doe');
//Set the subject line
$mail->Subject = 'PHPMailer SMTP test';
//Read an HTML message body from an external file, convert referenced images to embedded,
//convert HTML into a basic plain-text alternative body
$mail->msgHTML(file_get_contents('contents.html'), dirname(__FILE__));
//Replace the plain text body with one created manually
$mail->AltBody = 'This is a plain-text message body';
//Attach an image file
//$mail->addAttachment('images/phpmailer_mini.png');

//send the message, check for errors
if (!$mail->send()) {
    echo 'Mailer Error: ' . $mail->ErrorInfo;
} else {
    echo 'Message sent!';
}
?>