Description:
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I have found some inconsistencies in the behavior of debug_backtrace.  I'm not sure either of these are bugs, so I'm filing this under documentation.

1) If call_user_func is used, debug_backtrace output includes an array entry with no file/line info.  Seems to be the case with PHP versions as far back as 4.3.0.

debug_backtrace docs do say these are the "possible" values to be in the backtrace, but doesn't list any conditions where file/line might be omitted.  If this behavior in the debug_backtrace output is expected, then maybe document this here.

2) If an error handler is invoked, debug_backtrace output differs between PHP versions.  PHP 4.x has 2 entries (one with error handler and its params, another with file/line where error occurred).. PHP 5.1.x and 5.2.0RC5 combine these into a single entry (didn't text 5.0.x).  Maybe this is related, not sure: http://bugs.php.net/bug.php?id=34175

Perhaps this should be a ChangeLog entry on the docs page for debug_backtrace.


Reproduce code:
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<pre><?php
function my_func() { 1 / 0; }
function do_backtrace() { print_r(debug_backtrace()); }
set_error_handler('do_backtrace');
call_user_func('my_func');
?></pre>

Expected result:
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Output that can be predicted by reading the debug_backtrace docs.

Actual result:
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file/line missing for entry after call_user_func, and array length differs between PHP 4.x and 5.1.x/5.2.0.