Came across a nice overview / article about PCI Compliance while doing some research for work:
While this article is a very high-level overview of PCI concepts, it did link to a pretty interesting article regarding logging. Logging relates to PCI compliance because part of the spec requires all access to sensitive information (like credit card numbers) to be logged. The article links to a PHP-specific recommendation for standardized logging:
I had never heard of PSR-3 compliant logging before this, but I think I will try to implement this in all of my logging going forward.