Uh-oh. What if you see the PHP equivalent of the blue screen of death?
It may be no more than missing a . between concatenated strings -- which is how I got this to show up.
You may be able to fix it by putting flags -- like "flag1<br>" -- through the code, and noting the last one that gets printed. That often works.
If not, the only fix I know is to rip out about half your code and see if it fixes it. If it did, that's the problem; put half of that back in. (If not, it's the other half.) Using this, determine what line is the problem, and replace or repair it.