If you're thinking to do it with Wordpress then there is a plugin called
AffiliateWP with which you can create an affiliate program and then use cryptocurrencies once you added one of the
3rd party addon.
Many coins can be used and it uses coinmarketcap rates at the time of payments. Payments aren't automatic but it's supposed coming
Add multiple currencies and any Ethereum token to your AffiliateWP wallet.
Generate draft Payments from individual or bulk selected Referrals
Generate draft Payments from individual or bulk selected Affiliates.
Generate draft Payments for all Affiliates (one button to pay all).
Set Affiliate’s payment currency and payment address on their profile (edit affiliate form).
See Affiliate’s payment currency on the Affiliate’s list.
See the transaction status and explorer links on Payouts
Otherwise, I may be wrong but it's possible Gourl has a PHP script to do the same (more or less)
There are some fiat affiliate systems like Clickbank,JVZoo,Warriorplus,Digistore24,but I've never heard about a Bitcoin affiliate program that pays automatic commissions.
Out of topic with what the @OP is looking