<?php
class Mailer
{
    private static $instance;

    private function __construct()
    {
    }

// 不可以被克隆
    final public function __clone()
    {
        throw new Exception("RequestContext CANNOT clone! use 'instance' method");
    }

    public static function instance(){
        if (!isset(self::$instance)) {
            self::$instance = new Mailer();
        }

        return self::$instance;
    }

    /**
     * 发送邮件
     *
     * @param string $from      发送邮箱
     * @param string $to        收件邮箱
     * @param string $subject   主题
     * @param string $body      邮件内容，默认使用html
     *
     * @return bool
     */
    public function sendEmail(string $from, string $to, string $subject, string $body): bool
    {
        if( empty($from) || empty($to) ) {
            return false;
        }

        $mailer   = Yii::$app->mailer->compose();
        $mailer->setFrom($from);
        $mailer->setTo($to);
        $mailer->setSubject($subject);
        $mailer->setHtmlBody($body);
        $status     = $mailer->send();

        return $status;
    }

    public function ceshi(){
        echo 1111;
    }
}