debug_backtrace(): 'arg' contain current value instead of passing value

[WinterSilence]

Description

The following code:

<?php
class Test
{
    public function run(int $v)
    {
        $v = 2;
        var_export(debug_backtrace(limit: 1));
    }
}

(new Test())->run(1);

Resulted in this output:

array (
  0 => array (
    'file' => 'test.php',
    'line' => 12,
    'function' => 'run',
    'class' => 'Test',
    'object' => \Test::__set_state(array()),
    'type' => '->',
    'args' => array (0 => 2,),
  ),
)

But I expected this output instead:

array (
  0 => array (
    'file' => 'test.php',
    'line' => 12,
    'function' => 'run',
    'class' => 'Test',
    'object' => \Test::__set_state(array()),
    'type' => '->',
    'args' => array (0 => 1,),
  ),
)

From docs:

args If inside a function, this lists the functions arguments.

I.e. args must contain passed argument (1) instead current value of $v (2)

PHP Version

PHP 8.3.14 (cli) (built: Nov 20 2024 21:06:22) (ZTS Visual C++ 2019 x64)
Copyright (c) The PHP Group
Zend Engine v4.3.14, Copyright (c) Zend Technologies
with Zend OPcache v8.3.14, Copyright (c), by Zend Technologies

Operating System

Windows 11

[nielsdos]

This is something that has changed in PHP7. In PHP5 and lower this retained the original value, whereas now it reflects the new value. Changing this would mean backupping the old value, which would negatively affect performance. Furthermore, people may rely on the current behaviour so we can't just change this. I'm closing this as "won't fix".

[WinterSilence]

@nielsdos then how get initial/passed arguments?

[nielsdos]

You can't unless you store them somewhere at the start of the function.

[WinterSilence]

@nielsdos sadly, we can't real trace execution (

Changing this would mean backupping the old value, which would negatively affect performance
maybe add option to use old behavior? if it's not possible, then need add notice to documentation

[nielsdos]

What exactly are you trying to accomplish? Maybe there's another way?

[WinterSilence]

@nielsdos I use some external packages with code like as:

<?php
class Test
{
    public function run(ArrayObject $v)
    {
        $v = 2;
    }
}

(new Test())->run(new ArrayObject([1]));

Current behavior create problem with code trace at error because debug_backtrace() return ['v' => 2] in args and I can't easily understand what's values really passed in method. It's really hard when nesting level more than 10.

[nielsdos]

If the goal is to debug, then I recommend using a debugger like xdebug instead of dumping values. That'll allow you to see how the values evolve and set breakpoints/watchpoints etc

[WinterSilence]

@nielsdos ok, thanks. phpstorm not display it's (