I have build an subscription app, every thing is working fine
customer can purchase subscription plan and app receives the contract, using create billing attempt mutation i can create billing attempt and create order but i want to automate this process
can anyone help me in this ???
Hello @HD_WORK 
Thanks for reaching out. Shopify does not offer a mechanism to schedule and automate this process. The scheduling and the automation of billing attempts is the responsibility of the app developers. See: https://shopify.dev/tutorials/shopify-subscriptions-overview#division-of-responsibilities-between-shopify-and-apps
You need to run a recurring cron job that iterates through your subscriptions, check which ones are active & equal to or past the next billing date, and then call the charge subscription mutation.
can you guide me how can i setup cron job/schedular. i am using core php and mysql