要给新项目写一个注册功能，邮件认证是必须的，那就必须发邮件验证码

先是使用打乱数组制造验证码

/**
 * 获得随机字符串
 * @param $len             需要的长度
 * @param $special        是否需要特殊符号
 * @return string       返回随机字符串
 */
function getRandomStr($len, $special=true){
    $chars = array(
        "a", "b", "c", "d", "e", "f", "g", "h", "i", "j", "k",
        "l", "m", "n", "o", "p", "q", "r", "s", "t", "u", "v",
        "w", "x", "y", "z", "A", "B", "C", "D", "E", "F", "G",
        "H", "I", "J", "K", "L", "M", "N", "O", "P", "Q", "R",
        "S", "T", "U", "V", "W", "X", "Y", "Z", "0", "1", "2",
        "3", "4", "5", "6", "7", "8", "9"
    );

    if($special){
        $chars = array_merge($chars, array(
            "!", "@", "#", "$", "?", "|", "{", "/", ":", ";",
            "%", "^", "&", "*", "(", ")", "-", "_", "[", "]",
            "}", "<", ">", "~", "+", "=", ",", "."
        ));
    }

    $charsLen = count($chars) - 1;
    shuffle($chars);                            //打乱数组顺序
    $str = '';
    for($i=0; $i<$len; $i++){
        $str .= $chars[mt_rand(0, $charsLen)];    //随机取出一位
    }
    return $str;
}

调用函数只需要传返回字符串的长度即可

然后去了PHPMailer的官网试图安装PHPMailer/PHPMailer：PHP 的经典电子邮件发送库

然后发现需要Composer，我没有安装Composer，然后又去了Composer中文网

通过了全局安装Composer之后就可以了用composer命令了

下面安装PHPMailer

composer require phpmailer/phpmailer

然后在安装的根目录创建一个.php文件，写入以下示例代码

<?php
//将PHPMailer类导入全局命名空间
//这些必须在脚本的顶部，而不是在函数内部
use PHPMailer\PHPMailer\PHPMailer;
use PHPMailer\PHPMailer\SMTP;
use PHPMailer\PHPMailer\Exception;

//加载 Composer 的自动加载器
require 'vendor/autoload.php';

//创建一个实例； 传递 `true` 启用异常
$mail = new PHPMailer(true);

try {
    //Server settings
    $mail->SMTPDebug = SMTP::DEBUG_SERVER;                      //启用详细调试输出
    $mail->isSMTP();                                            //使用SMTP发送
    $mail->Host       = 'smtp.example.com';                     //设置SMTP服务器发送通过
    $mail->SMTPAuth   = true;                                   //启用SMTP认证
    $mail->Username   = 'user@example.com';                     //SMTP用户名
    $mail->Password   = 'secret';                               //SMTP密码
    $mail->SMTPSecure = PHPMailer::ENCRYPTION_SMTPS;            //启用隐式TLS加密
    $mail->Port       = 465;                                    //要连接的TCP端口； 如果您设置了 `SMTPSecure = PHPMailer::ENCRYPTION_STARTTLS`，请使用 587

    //收件人
    $mail->setFrom('from@example.com', 'Mailer');         //发件人
    $mail->addAddress('joe@example.net', 'Joe User');     //添加收件人
    //$mail->addAddress('ellen@example.com');             //名字是可选的
    $mail->addReplyTo('info@example.com', 'Information'); //添加回复到
    //$mail->addCC('cc@example.com');                     //添加CC
    //$mail->addBCC('bcc@example.com');                   //添加密件抄送

    /*附件
    $mail->addAttachment('/var/tmp/file.tar.gz');         //添加附件
    $mail->addAttachment('/tmp/image.jpg', 'new.jpg');    //可选的，附件名称
    */
    //内容
    $mail->isHTML(true);                                  //设置邮件格式为HTML
    $mail->Subject = 'Here is the subject';               //主题
    $mail->Body    = 'This is the HTML message body <b>in bold!</b>';  //内容
    $mail->AltBody = 'This is the body in plain text for non-HTML mail clients';  //这是非 HTML 邮件客户端的纯文本正文

    $mail->send();
    echo '信息已发送';
} catch (Exception $e) {
    echo "无法发送消息。 邮件错误： {$mail->ErrorInfo}";
}

填写了信息应该就可以了