Build bespoke reporting web application

I have a web application built in LAMP which I need to add reporting to - at the moment I have manually built a few reports but customers are asking for specific reports which they want/need so I would like to explore giving them the option of designing and building their own totally custom reports.

The system will need to be web based so when they login they can start to build their reports - they should be able to pick a table/tables, fields, display options and so on and then save the report for their use ONLY. The report should be able to be viewed on screen, printed or exported as PDF/CSV etc.

This needs to fully integrate into the existing application including access and security etc.

Please send questions directly to me and I will do my best to answer.