What are some good examples of a first PHP app to build for someone who is learning?
My answer to What are some good examples of a first PHP app to build for someone who is learning? on Quora
Build a blog. Blog engines are, in my opinion, the ideal starter project for learning any server-side web technology.
They can be incredibly simple (just a reverse ordered list of posts—a single SQL query) and can be useful after implementing a tiny subset of functionality—but they offer almost limitless scope for extension and learning new things.
Start with a single entries table and homepage. Now add a form for adding new entries. Then add edit and delete functionality. Add a simple login mechanism.
Next, add tags (and learn about many-to-many database tables). Add pagination or month/year based archives.
Next, an Atom feed (learning about syndication and XML output in the process).
Add comments—and learn about XSS and other issues involved in accepting user-entered content.
A blog engine us a great learning project because it can be as simple or complicated as you like.