i want to use cron job for my project for sending emails, i have searched google but i dont found anything yet. anyone knows how to achieve it . Your help is appreciated Thank you

Just make a php script that does what you need. Then add a line in your crontab on your hosting server to execute the file on an interval of your choosing.

Which of those parts do you have an issue with? If it's your email script, post it and tell us exactly what the issue is.

If it's the cron part, tell us what host you have and what control panel, and people can help you resolve that issue.