[php-src] Issue #13231: foreach(readonly)

Issue: https://github.com/php/php-src/issues/13231 Author: SVGAnimate ### Description This code should be able to stop before crashing. ```PHP <?php $fib = [0, 1]; foreach($fib as $n=>$fib_n) { $fib[] = $fib[$n] + $fib[$n+1];// ! \ $fib is readonly / ! \\ } print_r($fib); ``` But in this way, it is not intuitive : security is minimal. I would have preferred to be notified by a warning ``` Array ( [0] => 0 [1] => 1 [2] => 1 [3] => 2 ) ``` <hr /> As in many other languages, variables declared in a foreach are not writable. In PHP we can modify this behavior thanks to the reference operator `&` However, there is a difference between being able to modify the content and the container. Also, I would like to know how you perceive this type of writing: ```PHP <?php foreach(&$fib = [0, 1] as $value) { $fib[] = $fib[$n] + $fib[$n+1]; } print_r($fib);// [0,1, 1, 2, 3, 5, 8, ...] ``` Or perhaps in the other way, more tedious, less coherent, more dangerous ```PHP <?php $init = [0, 1]; $fib = &$init; foreach(readonly $fib as $value) { $fib[] = $fib[$n] + $fib[$n+1]; } print_r($fib);// [0,1, 1, 2] Stoped at count($__fib); $fib=[0, 1]; foreach([0, 1] as $value) { $fib[] = $fib[$n] + $fib[$n+1]; } print_r($fib);// [0,1, 1, 2] Stoped at count([0, 1]); ```