Database/Storage engine suggestion for a project involving heavy inserts?
Let's break this question up into a few parts.

Q: I need to insert 1mm rows a day. Is that a lot?

Not really. 1mm divided by 24 hours divided by 60 minutes divided by 60 seconds gives you about 12 inserts per second. For a rough frame of perspective, it's not unusual to see 1,000 inserts per second in typical commodity servers with no tuning.

Granted, your load won't be perfectly averaged out like that - you'll have bursts of load - but I wouldn't make database platform decisions based on less than 10k-20k inserts per second. Any platform out there will work fairly well.

Q: How should I structure the data?

Zoom out - don't think table, think databases. If you're going to be keeping this data permanently, and it's truly insert-only with no updates, then you probably want to start a new database for time lengths. Your inserts may only go into one table in one database, but every year, create a new database (MyApp_2015) and seal the old 2014 data as read-only. You can stop backing it up (as long as you've still got a good backup once), stop doing index maintenance, statistics updates, etc.

The PHP will only ever have to know about the current database for inserts, making your design a lot easier. The archival process becomes a DBA task much later down the road as long as you go in knowing that there will be more than one database involved.

If you were doing more than 1,000 inserts per second sustained, and you wanted easier performance management, then I'd also suggest building sharding into the initial design regardless of the database platform. Don't get me wrong, any modern database can handle over 1,000 inserts per second, but designing sharding in now just gives you more flexibility later on. At 12 inserts per second, it's just not worth the design/testing hassle.

Q: How should I do reporting?

In an ideal world, reports would not be done against the live server. Run the reports against a restored or replicated copy of the database. This does two things: it reduces load on the live server, and it validates your backups, guaranteeing that you've got your valuable data elsewhere.