MySQL on RDS, data transfer from one instance to another as a production job
MySQL RDS allows you to do two options
OPTION #1
You set up a Read Slave. Then, run the reports from it. There is a tool in the RDS CLI called rds-create-db-instance-read-replica to create a Read Slave from a Running RDS instance. The following are done under the hood:

Snapshot Made
Snapshot Brought Up
CHANGE MASTER TO executed with proper binary log and position

OPTION #2
Take a live snapshot of Production. Then, open a new instance using that snapshot.
The tools for this are

rds-create-db-snapshot
rds-restore-db-instance-from-db-snapshot

CONCLUSION
The only difference between these options

the Read Slave is continuous
Snaphot brought up as a point-in-time Instance

In both cases, once you done, simply drop the new Instance (saves money) at your discretion.
If you combine the two ideas, you could load your PHP script's output into the point-time instance. Any needed data to retrieve from production could be read from the Read Slave to prevent further load issues with production.
WARNING
Bringing up instances can be time-consuming. So, plan to have the instance brought up early enough for report and import time.
This is more ranting and brainstorming than a concrete answer.