At Physio Effect we use Stripe to process payments in our shop
Stripe has been audited by a PCI-certified auditor and is certified to PCI Service Provider Level 1.
This is the most stringent level of certification available in the payments industry. To accomplish this, Stripe make use of best-in-class security tools and practices to maintain a high level of security.
If you'd like to know more about Stripe's security, please feel free to look on their website here