Look at this from the perspective of what roles did you play in the project:
Business Analysis - Did you gather any requirements? Did you clarify anything that had to be done?
Solution Architecture - Did you play a role in mapping out the solution and what technologies would be used? Did you test out possible alternative stacks?
Development work - This would be the actual implementation work you did.
Testing - Did you do any Quality Assurance, unit tests and so forth?
Deployment and Maintenance - Did you put this into production or have tasks around promoting the code through various environments?
What were the specific tasks you did, with what technologies and over what time frame would be how I'd frame this for the resume and job interview as chances are this will be something to discuss at that point.
Backend + Frontend Developer for a web portal with SQL/PHP/jQuery (no CSS design experience)
Unless you did any of the things JB King mentions to a larger extent, that should cover it pretty well and people know what experience to expect when they hire you.
Replace SQL with the database you used, Postgres, MySQL, Mongo, even the SQL ones are all different in syntax, etc.