array_walk with printf callback bypasses TypeError for non-string format

[sanmai]

Description

The following code:

<?php declare(strict_types=1);

$input = [1, 2, 3];
array_walk($input, printf(...));

Resulted in this output:

123

But I expected this output instead:

Fatal error: Uncaught TypeError: printf(): Argument #1 ($format) must be of type string, int given

By comparison, this code throws as expected:

<?php declare(strict_types=1);

$input = [1, 2, 3];
foreach ($input as $k => $i) {
    printf($i, $k);
}

PHP Version

PHP 8.4.10 (cli) (built: Jul  3 2025 12:35:27) (NTS)
Copyright (c) The PHP Group
Built by Debian
Zend Engine v4.4.10, Copyright (c) Zend Technologies
    with Zend OPcache v8.4.10, Copyright (c), by Zend Technologies
    with Xdebug v3.4.2, Copyright (c) 2002-2025, by Derick Rethans

Operating System

No response

[nielsdos]

strict_types has no influence on scalar type coercion for functions called by the engine.
This is one of the weird things of strict types.
If you want to learn more about this, Gina has done multiple talks about strict types and what it does/does not do.