什么'；这里错了吗?(新手）

在实际发送电子邮件之前，我需要检查是否有互联网连接。在我添加以下代码和函数之前，一切都很好：

if(doesConnectionExist())
{
    $errors .= "'n No internet connection!";
}

加上这个功能：

function doesConnectionExist
{
    var xhr = new XMLHttpRequest();
    var file = "http://www.?????.com/somefile.png";
    var randomNum = Math.round(Math.random() * 10000);
    xhr.open('HEAD', file + "?rand=" + randomNum, false);
    try {
        xhr.send();
        if (xhr.status >= 200 && xhr.status < 304) {
            return true;
        } else {
            return false;
        }
    } catch (e) {
        return false;
    }
}

总代码如下所示：

<?php 
header ('Content-type: text/html; charset=iso8859-15');
$your_email ='????@????.com';
session_start();
$errors = '';
$firstname = ' ';
$lastname = '';
$visitor_email = '';
if(isset($_POST['submit']))
{
$firstname = $_POST['firstname'];
$lastname = $_POST['lastname'];
$visitor_email = $_POST['email'];
if(empty($firstname)||empty($lastname)
{
    $errors .= "'n firstname and lastname are required fields. ";   
}

if(doesConnectionExist())
{
    $errors .= "'n No internet connection!";
}

if(empty($errors))
{
    $to = $your_email;
    $subject="test";
    $from = $your_email;
    $body = "test'n".
    "Firstname: $firstname'n".
    "Lastname: $lastname 'n".
    $headers = "Reply-To: $visitor_email 'r'n";
    mail($to, $subject, $body, $headers);
    header('Location: thankyou.html');
}
}
function doesConnectionExist
    {
    var xhr = new XMLHttpRequest();
    var file = "http://www.?????.com/somefile.png";
    var randomNum = Math.round(Math.random() * 10000);
    xhr.open('HEAD', file + "?rand=" + randomNum, false);
    try {
        xhr.send();
        if (xhr.status >= 200 && xhr.status < 304) {
            return true;
        } else {
            return false;
        }
    } catch (e) {
        return false;
    }
}
?>

如果有人能帮助我，那就太好了！提前谢谢。