There's lots of possible problems, but does it work ok?
At the very least we need to know more about the light panel and the pir.
Slowly changing light levels could easily make the middle transistor get quite hot when the LDR is triggered on.
The voltage drop across the two transistors on the right could cause the panel not to reach full brightness.
You don't have a base resistor for the transistor on the right. Normally this is a requirement, but if the PIR is capable of only a small output current and doesn't mind the near short across it, then that's fine too.
You don't show a power supply, but I assume one is connected!
The fact that I (and many others here) may have done it differently (and maybe better) is not an issue if the circuit works and the drawbacks are not an issue.