Improved Bug Report for "header already sent" warning

[ianwhiteley]

WARNING RECEIVED
PHP Warning: session_start(): Cannot start session when headers already sent in /filepath on line xx

CURRENT SCENARIO & ISSUE
This warning gives the line number xx of the session_start(). It does not tell you WHAT triggered the sending of headers before this point was reached, and where that point is.

REQUESTED IMPROVEMENT
Add the file / line number for WHEN the last headers were previously sent - as this can be very difficult to pinpoint.