$to = '收件人邮箱';

$subject = '邮件主题';

$message = '邮件内容';

$from = '发件人邮箱';

$headers = "From: $from" . "

" . "Reply-To: $from" . "

" . "X-Mailer: PHP/" . phpversion();

mail($to, $subject, $message, $headers);

use PHPMailerPHPMailerPHPMailer;

use PHPMailerPHPMailerException;

require 'vendor/autoload.php';

// 实例化PHPMailer类

$mail = new PHPMailer(true);

try {

    // 服务器配置

    $mail->isSMTP();

    $mail->Host = 'smtp.gmail.com';

    $mail->SMTPAuth = true;

    $mail->Username = '你的Gmail邮箱';

    $mail->Password = '你的Gmail邮箱密码';

    $mail->SMTPSecure = 'tls';

    $mail->Port = 587;

    // 收件人信息

    $mail->setFrom('发件人邮箱', '发件人名称');

    $mail->addAddress('收件人邮箱', '收件人名称');

    // 邮件内容

    $mail->isHTML(true);

    $mail->Subject = '邮件主题';

    $mail->Body    = '邮件内容';

    // 发送邮件

    $mail->send();

    echo '邮件发送成功！';

} catch (Exception $e) {

    echo '邮件发送失败: ', $mail->ErrorInfo;

}