PHP-发送电子邮件HTML/纯文本-语法错误

我正在尝试实现一个简单的sendEmails函数，如果可能的话，它会发送HTML，如果不可能的话它会发送纯文本。然而，由于某种原因，我在文件中遇到了语法错误，即使我通过在线验证器（如phpcodechecker）传递它，它也不会出现任何问题。

准确的错误：

分析错误：语法错误，C:''examplep''htdocs中出现意外的文件结尾。。''第83行上的func.php

注意：我只实现了sendEmails功能，它破坏了它

我的代码

<?php
    //Input: Email | Output: Boolean for Domain Existence (such as @yahoo.com) [TESTED]
    function domainExists($email, $record = 'MX'){
        list($user, $domain) = explode('@', $email);
        return checkdnsrr($domain, $record);
    }
    function sendEmails($to, $type, $link){
        switch($type){
            case "register":
                if(strlen($link)>0) $authenticationLink = $link;
                else throwError("Email Failed",1);
                //Send Email
                $subject = "Thank You For Registering";
                $boundaryHash = md5(date('r',time()));
                $headers = "From: admin@....com";
                $headers .= "'r'nContent-Type: multipart/alternative; boundary='"PHP-alt-".$boundaryHash."'"";
                ob_start();
                ?>
                    --PHP-alt-<?php echo $boundaryHash; ?> 
                    Content-Type: text/plain; charset="iso-8859-1"
                    Content-Transfer-Encoding: 7bit
                    Thank you for registering with ...! 
                    We hope you enjoy our service! To get started, please authenticate your account by copying and pasting the following link:
                    <?php echo $authenticationLink; ?>
                    --PHP-alt-<?php echo $boundaryHash; ?> 
                    Content-Type: text/html; charset="iso-8859-1"
                    Content-Transfer-Encoding: 7bit
                    <h2>Thank You For Registering!</h2>
                    <p>Thank you for registering with ...!</p>
                    <p>We hope you enjoy our service! To get started, please authenticate your account with the following link:</p>
                    <a href="<?php echo $authenticationLink; ?>">Click to Authenticate</a>
                    --PHP-alt-<?php echo $boundaryHash; ?>--
                <?
                $message = ob_get_clean();
                $mail_sent = mail( $to, $subject, $message, $headers );
                echo $mail_sent ? "Mail sent" : "Mail failed";
                break;
            default: break;
        }
        return;
    }
    //isEscaped(String, Con):boolean, [TESTED]
    function isEscaped($str, $con){
        return (mysqli_real_escape_string($con, $str) === $str);
    }

    //Type: | 0: Unknown Error | 1:  | 2: DB Error | 3: Security Issue - Unescaped |
    //String: | 'Fatal' | 'NonFatal' | 'Trivial' | Otherwise String will be output
    //[TESTED]
    function throwError($str, $type){
        //Making sure parameters are valid
        $t = (int)$type; 
        $s = (string)$str;  
        //Shorthand to auto output general errors
        switch ($s){ 
            case 'Fatal': 
                $s = "FATAL ERROR: Please contact the administrator immediately!"; 
                break;
            case 'NonFatal':
                $s = "ERROR: Please contact the administrator!";
                break;
            case 'Trivial':
                $s = "Unexpected Error: Please go back and try again!";
                break;
        }
        echo "<p class='errorspan'>".$s.": ".$t."</p>";
        exit($t);
    }?>