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 with as little effort as possible.

Is there a tool/program/command/IDE that can, on PHP script termination, tell you the location of a script exit?

Note: I can't mark my own post as "accepted answer" so look at the bottom to see my solution. If you come up with a better solution I will mark your post as the answer.

Answer 1

I use the following code and need no special debugging environment. Note that this might take really long; you can set the ticks count higher - that makes it faster, but blurry.

function shutdown_find_exit()
{
    var_dump($GLOBALS['dbg_stack']);
}
register_shutdown_function('shutdown_find_exit');
function write_dbg_stack()
{
    $GLOBALS['dbg_stack'] = debug_backtrace();
}
register_tick_function('write_dbg_stack');
declare(ticks=1);

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

grep -n die filename

Answer 4

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

Answer 5

Add this to the top of the file:

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


register_shutdown_function('shutdown');

See register_ shutdown_function()

Answer 6

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 7

xdebug has a nice trace feature that'll allow you to see all the entire trace of your php app execution and it should give you give clue as to where your exit is.

but for the quick and dirty solution a grep/find as mentioned above will do rightly.

Answer 8

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.

Answer 9

Make sure that errors are displayed in your development environment (not production).