can't run php bot.php

[skyee01]

i have follow the instruction, but after i run php bot.php in my cmd appear this message

Fatal error: Uncaught exception 'Exception' with message 'Error when requesting
https://slack.com/api/rtm.start SSL certificate problem: unable to get local iss
uer certificate' in C:\xampp\htdocs\php-slack-bot-with-simsimi-master\vendor\jcl
g\php-slack-bot\src\PhpSlackBot\Bot.php:143
Stack trace:
#0 C:\xampp\htdocs\php-slack-bot-with-simsimi-master\vendor\jclg\php-slack-bot\s
rc\PhpSlackBot\Bot.php(55): PhpSlackBot\Bot->init()
#1 C:\xampp\htdocs\php-slack-bot-with-simsimi-master\bot.php(94): PhpSlackBot\Bo
t->run()
#2 {main}
thrown in C:\xampp\htdocs\php-slack-bot-with-simsimi-master\vendor\jclg\php-sl
ack-bot\src\PhpSlackBot\Bot.php on line 143

what should i do next?