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PHP 功能完整的 Email 發送類：支援純文字、HTML、附件、抄送、密件副本

編輯：PHP 綜合知識

類別結構概覽

屬性：收件人、抄送、密件副本、寄件人、主題、文字內容、HTML 內容、附件路徑
方法：setTo()、setCC()、setBCC()、setFrom()、setSubject()、setText()、setHTML()、setAttachments()、send()
內部：MIME 多部分組裝、Base64 附件編碼、樣板載入、隨機邊界產生

核心程式碼 (節錄關鍵方法)

<?php
class Email {
    public $mailTo = ''; public $mailCC = ''; public $mailBCC = '';
    public $mailFrom = ''; public $mailSubject = '';
    public $mailText = ''; public $mailHTML = ''; public $mailAttachments = '';

    // 共用地址驗證
    private function checkEmail($addr) {
        return (bool)preg_match('/^[^@]+@([a-zA-Z0-9-]+\.)+[a-zA-Z]{2,}$/', $addr);
    }

    public function setTo($addr) {
        foreach (explode(',', $addr) as $a) if (!$this->checkEmail(trim($a))) return false;
        $this->mailTo = implode(',', array_map('trim', explode(',', $addr)));
        return true;
    }
    // setCC, setBCC, setFrom, setSubject, setText, setHTML, setAttachments 類似...

    // MIME 組裝核心
    private function getRandomBoundary($offset=0) {
        srand(time() + $offset);
        return "----" . md5(rand());
    }

    private function getContentType($file) {
        $ext = strtolower(pathinfo($file, PATHINFO_EXTENSION));
        $map = [
            'gif'=>'image/gif', 'jpg'=>'image/jpeg', 'jpeg'=>'image/jpeg',
            'png'=>'image/png', 'txt'=>'text/plain', 'html'=>'text/html',
            'htm'=>'text/html', 'zip'=>'application/zip', 'gz'=>'application/gzip',
            'pdf'=>'application/pdf',
        ];
        return $map[$ext] ?? 'application/octet-stream';
    }

    public function send() {
        $headers = "";
        if ($this->mailCC)   $headers .= "CC: {$this->mailCC}\r\n";
        if ($this->mailBCC)  $headers .= "BCC: {$this->mailBCC}\r\n";
        if ($this->mailFrom) $headers .= "From: {$this->mailFrom}\r\n";

        // 純文字
        if ($this->mailText && !$this->mailHTML && !$this->mailAttachments) {
            return mail($this->mailTo, $this->mailSubject, $this->mailText, $headers);
        }

        // 文字 + HTML (multipart/alternative)
        if ($this->mailText && $this->mailHTML && !$this->mailAttachments) {
            $boundary = $this->getRandomBoundary();
            $headers .= "MIME-Version: 1.0\r\n";
            $headers .= "Content-Type: multipart/alternative; boundary=\"$boundary\"\r\n\r\n";
            $body  = "--$boundary\r\n";
            $body .= "Content-Type: text/plain; charset=utf-8\r\n\r\n{$this->mailText}\r\n";
            $body .= "--$boundary\r\n";
            $body .= "Content-Type: text/html; charset=utf-8\r\n\r\n{$this->mailHTML}\r\n";
            $body .= "--$boundary--";
            return mail($this->mailTo, $this->mailSubject, $body, $headers);
        }

        // 文字 + HTML + 附件 (multipart/mixed)
        if ($this->mailText && $this->mailHTML && $this->mailAttachments) {
            $outer = $this->getRandomBoundary();
            $inner = $this->getRandomBoundary(1);
            $headers .= "MIME-Version: 1.0\r\n";
            $headers .= "Content-Type: multipart/mixed; boundary=\"$outer\"\r\n\r\n";
            $headers .= "This is a multi-part message in MIME format.\r\n";
            $headers .= "--$outer\r\n";
            $headers .= "Content-Type: multipart/alternative; boundary=\"$inner\"\r\n\r\n";
            $headers .= "--$inner\r\n";
            $headers .= "Content-Type: text/plain; charset=utf-8\r\n\r\n{$this->mailText}\r\n";
            $headers .= "--$inner\r\n";
            $headers .= "Content-Type: text/html; charset=utf-8\r\n\r\n{$this->mailHTML}\r\n";
            $headers .= "--$inner--\r\n";

            foreach (explode(',', $this->mailAttachments) as $file) {
                $file = trim($file);
                $headers .= "--$outer\r\n";
                $ctype = $this->getContentType($file);
                $headers .= "Content-Type: $ctype; name=\"".basename($file)."\"\r\n";
                $headers .= "Content-Transfer-Encoding: base64\r\n";
                $headers .= "Content-Disposition: attachment; filename=\"".basename($file)."\"\r\n\r\n";
                $content = chunk_split(base64_encode(file_get_contents($file)));
                $headers .= $content . "\r\n";
            }
            $headers .= "--$outer--";
            return mail($this->mailTo, $this->mailSubject, "", $headers);
        }
        return false;
    }
}
?>

使用範例

<?php
require 'Email.php';
$mail = new Email();
$mail->setTo("user@example.com");
$mail->setCC("cc1@example.com, cc2@example.com");
$mail->setBCC("bcc@example.com");
$mail->setFrom("system@example.com");
$mail->setSubject("測試郵件");
$mail->setText("這是純文字內容");
$mail->setHTML("<h1>這是<b>HTML</b>內容</h1>");
$mail->setAttachments("/path/to/file.pdf, /path/to/image.png");
if ($mail->send()) echo "寄送成功";
else echo "寄送失敗";
?>

現代化建議

內建 mail() 依賴本地 MTA，易被視為垃圾郵件；生產環境建議改用 PHPMailer、Symfony Mailer、Laravel Mail 等透過 SMTP (含 SSL/TLS、認證) 發送。
附件編碼改用 base64_encode() 而非外部 uuencode，跨平台相容性更好。
加入 DKIM、SPF、DMARC 設定提升送達率。