PHP: rfc:func_get_args_by_name

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====== PHP RFC: Add func_get_args_by_name() ======

  * Version: 1.0
  * Date: 2025-12-02
  * Author: Alexandre Daubois <alexandredaubois@php.net>
  * Status: Under Discussion
  * Implementation: https://github.com/php/php-src/pull/19329
  * Target Version: PHP 8.6

===== Introduction =====

This RFC proposes adding a new <php>func_get_args_by_name()</php> function that returns all function arguments with their parameter names preserved as array keys, unlike <php>func_get_args()</php> which returns only positional arguments.

<PHP>
<?php
function greet(string $name, int $age, ...$extra): array {
    return func_get_args_by_name();
}

var_dump(greet('Alice', 30, 'foo', 'bar'));
// array(4) {
//   ["name"]=> string(5) "Alice"
//   ["age"]=> int(30)
//   [2]=> string(3) "foo"
//   [3]=> string(3) "bar"
// }
?>
</PHP>

With named arguments becoming widely used since PHP 8.0, this function provides a straightforward way to introspect function calls while preserving argument names.

===== Motivation =====

Currently, there is no built-in way to retrieve function arguments with their parameter names. The existing <php>func_get_args()</php> returns only positional values, and <php>func_get_arg()</php> requires knowing the position index. The only way to get named arguments is through reflection, which is verbose:

<PHP>
<?php
function example($a, $b) {
    $reflection = new ReflectionFunction(__FUNCTION__);
    $params = $reflection->getParameters();
    $args = func_get_args();
    $result = [];
    foreach ($params as $i => $param) {
        if (isset($args[$i])) {
            $result[$param->getName()] = $args[$i];
        }
    }
    return $result;
}
?>
</PHP>

The proposed <php>func_get_args_by_name()</php> eliminates this complexity and makes argument introspection straightforward.

===== Proposal =====

Add a new <php>func_get_args_by_name()</php> function to PHP. This function:

  * Returns an array where keys are parameter names and values are the passed arguments
  * Includes variadic arguments, which receive numeric keys if passed positionally, or named keys if passed via spread operator

**Key Difference from func_get_args():**

When using the spread operator with named arguments, <php>func_get_args_by_name()</php> captures extra named arguments that <php>func_get_args()</php> discards:

<PHP>
<?php
function process(string $name, int $age, ...$extra) {
    return func_get_args();
}

var_dump(process(...[
    'age' => 30,
    'name' => 'John',
    'extra' => 'data',
]));
// array(2) {
//   [0]=> string(4) "John"
//   [1]=> int(30)
// }
// 'extra' is missing

function process_named(string $name, int $age, ...$extra) {
    return func_get_args_by_name();
}

var_dump(process_named(...[
    'age' => 30,
    'name' => 'John',
    'extra' => 'data',
]));
// array(3) {
//   ["name"]=> string(4) "John"
//   ["age"]=> int(30)
//   ["extra"]=> string(4) "data"
// }
?>
</PHP>

===== Backward Incompatible Changes =====

This RFC introduces a new function without modifying existing functionality. Userland code declaring a function in the global namespace using this name would not work anymore, but a quick search on GitHub with the proposed function name revealed **no result**.

===== Proposed PHP Version =====

PHP 8.6 (next minor version)

===== Voting Choices =====

This is a simple yes/no vote requiring a 2/3 majority.

<doodle title="Add func_get_args_by_name() to PHP 8.6?" voteType="single" closed="false">
   * Yes
   * No
   * Abstain
</doodle>

Vote will start on [TBD] and end on [TBD].

===== References =====

  * Implementation PR: https://github.com/php/php-src/pull/19329
  * Discussion thread: [TBD]
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