Final or Readonly Local Variables

[peterujah]

Description

It would be helpful if PHP supported a way to declare local variables as final or readonly, especially in dynamic include contexts. This could prevent accidental override of values in files brought in via include or require.

Example:

function load(string $file): void {
    final $config = ['foo' => 'bar'];
    include $file; // Would throw an error if $config is reassigned.
}

Function:

init_with_scope(function(){
    // Access extracted immutable variables
}, mixed: ['config' => $config]);

This could improve safety when including untrusted or dynamic files, and align with practices of immutability. I understand this could require significant changes to the language internals, but I think it's worth discussing whether something similar (even limited to function scope) could be feasible without hacking immutability.

[nielsdos]

This is a language change, even with new syntax changes, and therefore needs an RFC.
Please see https://wiki.php.net/rfc/howto

[gncdev]

use define or const instead of final