Description:
------------
If a function modifies one of its parameters internally (not via reference), the argument list returned by the backtrace functions reflects the modification not the initial value.

The callstack arguments are being modified after the call is made.  Interestingly, this doesn't seem to affect functions which are using their default parameters.

Occurs in both debug_backtrace() and debug_print_backtrace()

Test script calls a pair of recursing functions — in the first, a parameter is passed to the top-most function normally.  In the second, the parameter's default value is used.

Stack entry #10 is modified in the first case and not in the second.

Test script:
---------------
<?php
echo "''\n";
foo('');

echo "\n\n";

echo "NULL\n";
foo();

function foo($str = '') {
    if (strlen($str) >= 30) {
        debug_print_backtrace();
        return;
    }

    $str .= 'foo';
    echo "'$str'\n";

    bar($str);
}

function bar($str) {
    $str .= 'bar';
    echo "'$str'\n";;

    foo($str);
}

Expected result:
----------------
''
'foo'
'foobar'
'foobarfoo'
'foobarfoobar'
'foobarfoobarfoo'
'foobarfoobarfoobar'
'foobarfoobarfoobarfoo'
'foobarfoobarfoobarfoobar'
'foobarfoobarfoobarfoobarfoo'
'foobarfoobarfoobarfoobarfoobar'
#0  foo(foobarfoobarfoobarfoobarfoobar) called at [/private/tmp/foo.php:26]
#1  bar(foobarfoobarfoobarfoobarfoo) called at [/private/tmp/foo.php:19]
#2  foo(foobarfoobarfoobarfoobar) called at [/private/tmp/foo.php:26]
#3  bar(foobarfoobarfoobarfoo) called at [/private/tmp/foo.php:19]
#4  foo(foobarfoobarfoobar) called at [/private/tmp/foo.php:26]
#5  bar(foobarfoobarfoo) called at [/private/tmp/foo.php:19]
#6  foo(foobarfoobar) called at [/private/tmp/foo.php:26]
#7  bar(foobarfoo) called at [/private/tmp/foo.php:19]
#8  foo(foobar) called at [/private/tmp/foo.php:26]
#9  bar(foo) called at [/private/tmp/foo.php:19]
#10 foo() called at [/private/tmp/foo.php:3]


NULL
'foo'
'foobar'
'foobarfoo'
'foobarfoobar'
'foobarfoobarfoo'
'foobarfoobarfoobar'
'foobarfoobarfoobarfoo'
'foobarfoobarfoobarfoobar'
'foobarfoobarfoobarfoobarfoo'
'foobarfoobarfoobarfoobarfoobar'
#0  foo(foobarfoobarfoobarfoobarfoobar) called at [/private/tmp/foo.php:26]
#1  bar(foobarfoobarfoobarfoobarfoo) called at [/private/tmp/foo.php:19]
#2  foo(foobarfoobarfoobarfoobar) called at [/private/tmp/foo.php:26]
#3  bar(foobarfoobarfoobarfoo) called at [/private/tmp/foo.php:19]
#4  foo(foobarfoobarfoobar) called at [/private/tmp/foo.php:26]
#5  bar(foobarfoobarfoo) called at [/private/tmp/foo.php:19]
#6  foo(foobarfoobar) called at [/private/tmp/foo.php:26]
#7  bar(foobarfoo) called at [/private/tmp/foo.php:19]
#8  foo(foobar) called at [/private/tmp/foo.php:26]
#9  bar(foo) called at [/private/tmp/foo.php:38]
#10 foo() called at [/private/tmp/foo.php:8]

Actual result:
--------------
''
'foo'
'foobar'
'foobarfoo'
'foobarfoobar'
'foobarfoobarfoo'
'foobarfoobarfoobar'
'foobarfoobarfoobarfoo'
'foobarfoobarfoobarfoobar'
'foobarfoobarfoobarfoobarfoo'
'foobarfoobarfoobarfoobarfoobar'
#0  foo(foobarfoobarfoobarfoobarfoobar) called at [/private/tmp/foo.php:26]
#1  bar(foobarfoobarfoobarfoobarfoobar) called at [/private/tmp/foo.php:19]
#2  foo(foobarfoobarfoobarfoobarfoo) called at [/private/tmp/foo.php:26]
#3  bar(foobarfoobarfoobarfoobar) called at [/private/tmp/foo.php:19]
#4  foo(foobarfoobarfoobarfoo) called at [/private/tmp/foo.php:26]
#5  bar(foobarfoobarfoobar) called at [/private/tmp/foo.php:19]
#6  foo(foobarfoobarfoo) called at [/private/tmp/foo.php:26]
#7  bar(foobarfoobar) called at [/private/tmp/foo.php:19]
#8  foo(foobarfoo) called at [/private/tmp/foo.php:26]
#9  bar(foobar) called at [/private/tmp/foo.php:19]
#10 foo(foo) called at [/private/tmp/foo.php:3]


NULL
'foo'
'foobar'
'foobarfoo'
'foobarfoobar'
'foobarfoobarfoo'
'foobarfoobarfoobar'
'foobarfoobarfoobarfoo'
'foobarfoobarfoobarfoobar'
'foobarfoobarfoobarfoobarfoo'
'foobarfoobarfoobarfoobarfoobar'
#0  foo(foobarfoobarfoobarfoobarfoobar) called at [/private/tmp/foo.php:26]
#1  bar(foobarfoobarfoobarfoobarfoobar) called at [/private/tmp/foo.php:19]
#2  foo(foobarfoobarfoobarfoobarfoo) called at [/private/tmp/foo.php:26]
#3  bar(foobarfoobarfoobarfoobar) called at [/private/tmp/foo.php:19]
#4  foo(foobarfoobarfoobarfoo) called at [/private/tmp/foo.php:26]
#5  bar(foobarfoobarfoobar) called at [/private/tmp/foo.php:19]
#6  foo(foobarfoobarfoo) called at [/private/tmp/foo.php:26]
#7  bar(foobarfoobar) called at [/private/tmp/foo.php:19]
#8  foo(foobarfoo) called at [/private/tmp/foo.php:26]
#9  bar(foobar) called at [/private/tmp/foo.php:38]
#10 foo() called at [/private/tmp/foo.php:8]