Hi Josh,
The Web Services API documentation does contain PHP samples. Please review:
https://success.clarizen.com/hc/en-us/articles/205711818-16-12-Web-Service-API-Guide-Version-2
Obviously you'll need the PHP SoapClient enabled.
The REST API does not contain any language/platform specific samples, because it's simply about sending well structured JSON messages through HTTP (and decoding the JSON results), so the documentation focuses in messages structure.
I suggest you Google "using rest api with php" (not Clarizen specific) to find some answers.
Hope this helps,
Ophir