[php-src] Issue #9697: `array_walk($ffiInstance, function () {})` crashes due to expecting mutable array

Issue: https://github.com/php/php-src/issues/9697 Author: TysonAndre ### Description The following code: ```php <?php $x = FFI::new('int'); array_walk($x, function($x) { echo "test\n"; }); ``` Resulted in this output: ``` segmentation fault (core dumped) ``` valgrind output: ``` ==73944== Process terminating with default action of signal 11 (SIGSEGV) ==73944== Bad permissions for mapped region at address 0x1D0352A ==73944== at 0xA8A598: zend_hash_iterator_add (zend_hash.c:503) ==73944== by 0x840B07: php_array_walk (array.c:1286) ==73944== by 0x84183B: zif_array_walk (array.c:1407) ==73944== by 0xAB4919: ZEND_DO_ICALL_SPEC_RETVAL_UNUSED_HANDLER (zend_vm_execute.h:1250) ==73944== by 0xB2B883: execute_ex (zend_vm_execute.h:55975) ==73944== by 0xB310D5: zend_execute (zend_vm_execute.h:60343) ==73944== by 0xA73DE2: zend_execute_scripts (zend.c:1780) ==73944== by 0x9CD491: php_execute_script (main.c:2480) ==73944== by 0xBEDD26: do_cli (php_cli.c:964) ==73944== by 0xBEE9E5: main (php_cli.c:1333) ``` But I expected this output instead: ```php // blank output ``` To fix this: array_walk expects get_properties to return a non-empty refcounted array. Options include: 1. Start doing that, e.g. with rebuild_object_properties. Also start to override the get_properties_for handler alongside the get_properties handler to return null 2. Change behavior of that and other callers of Z_OBJPROP and other uses of get_properties to allow internal classes to return null in handler overrides 3. Special case zend_hash_num_elements(target_hash) == 0 and return early while continuing to free userdata - this should avoid this crash? ```c // ext/standard/array.c // static int php_array_walk( // php_array_walk_context *context, zval *array, zval *userdata, int recursive) zend_hash_internal_pointer_reset_ex(target_hash, &pos); ht_iter = zend_hash_iterator_add(target_hash, pos); // this tries to modify the immutable array ``` ```c // ext/ffi/ffi.c static HashTable *zend_fake_get_properties(zend_object *obj) /* {{{ */ { return (HashTable*)&zend_empty_array; // This is a const immutable array } /* }}} */ ``` ### PHP Version 7.4-8.3-dev ### Operating System Any