Fastest way to determine where PHP script exits

Question

Say you have a large PHP project and suddenly, when attempting to run it, you just end up with a blank page. The script terminates and you want to find exactly where that is

Answer 1

Don't forget to grep for "exit" too.

Answer 2

With some inspiration from the nonworking but still right-direction answer from RoBorg, I used the following code in the beginning:

function shutdown() {
    global $dbg_stack_a;
    print_r($dbg_stack_a);
}
register_shutdown_function('shutdown');

And then I made a global conditional breakpoint (global = breakpoint is evaluated on each row), exploiting the fact that it can run code trough eval(), with the following "condition":

eval('
global $dbg_stack_a, $dbg_stack_b, $dbg_stack_c;
$dbg_stack_a = $dbg_stack_b;
$dbg_stack_b = $dbg_stack_c;
$dbg_stack_c = debug_backtrace();
return false;
')

Probably not fast but does the trick! Using this I was able to determine the exact file and line location that raised die(). (This example works in NuSphere.)

Answer 3

Add this to the top of the file:

function shutdown()
{
    print_r(debug_backtrace());
}


register_shutdown_function('shutdown');

See register_ shutdown_function()

Answer 4

grep -n die filename

Answer 5

You can use an interactive debugger to step through the code until you reach the exit point. Other than that, I think you're down to grep'ing the code for exit|die.

Answer 6

Also check the error___logs for "memory_limit" errors in the Apache error_log.

Memory Limit >= 10M Warning: (Set this to 10M or larger in your php.ini file)

In my experience, scripts suddenly end without warning or notice when this happens.