Using null as an array offset is not deprecated #20194

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1. thomas-0816

   added

   Bug

   Status: Needs Triage

   on Oct 16, 2025
2. ndossche

   assigned

   Girgias

   on Oct 16, 2025
3. ndossche commented on Oct 18, 2025

   

   ndossche

   on Oct 18, 2025

   Last edited by ndossche

   Member

   More actions

   Probably this, but I again don't like how deprecations in the core propagate through everything and make things more complicated than they should be.
   Not sure yet if the changes in zend_try_ct_eval_array are necessary, i.e. if we're allowed to emit a deprecation even for non-executed code?

   diff --git a/Zend/Optimizer/sccp.c b/Zend/Optimizer/sccp.c
   index bbf52d8cf69..38a28dcd488 100644
   --- a/Zend/Optimizer/sccp.c
   +++ b/Zend/Optimizer/sccp.c
   @@ -1106,6 +1106,11 @@ static void sccp_visit_instr(scdf_ctx *scdf, zend_op *opline, zend_ssa_op *ssa_o
    
    			if (op2) {
    				SKIP_IF_TOP(op2);
   +				if (Z_TYPE_P(op2) == IS_NULL) {
   +					/* Emits deprecation at run-time. */
   +					SET_RESULT_BOT(result);
   +					return;
   +				}
    			}
    
    			/* We want to avoid keeping around intermediate arrays for each SSA variable in the
   diff --git a/Zend/zend_API.c b/Zend/zend_API.c
   index 1b97974686e..4065e7a8618 100644
   --- a/Zend/zend_API.c
   +++ b/Zend/zend_API.c
   @@ -2256,6 +2256,7 @@ ZEND_API zend_result array_set_zval_key(HashTable *ht, zval *key, zval *value) /
    			result = zend_symtable_update(ht, Z_STR_P(key), value);
    			break;
    		case IS_NULL:
   +			zend_error(E_DEPRECATED, "Using null as an array offset is deprecated, use an empty string instead");
    			result = zend_hash_update(ht, ZSTR_EMPTY_ALLOC(), value);
    			break;
    		case IS_RESOURCE:
   diff --git a/Zend/zend_compile.c b/Zend/zend_compile.c
   index b51a519533c..e31bc28affa 100644
   --- a/Zend/zend_compile.c
   +++ b/Zend/zend_compile.c
   @@ -10259,13 +10259,14 @@ static bool zend_try_ct_eval_array(zval *result, zend_ast *ast) /* {{{ */
    					zend_hash_index_update(Z_ARRVAL_P(result), 1, value);
    					break;
    				case IS_NULL:
   -					zend_hash_update(Z_ARRVAL_P(result), ZSTR_EMPTY_ALLOC(), value);
   -					break;
   +					/* Null key will generate a warning at run-time. */
   +					goto fail;
    				default:
    					zend_error_noreturn(E_COMPILE_ERROR, "Illegal offset type");
    					break;
    			}
    		} else if (!zend_hash_next_index_insert(Z_ARRVAL_P(result), value)) {
   +fail:
    			zval_ptr_dtor_nogc(value);
    			zval_ptr_dtor(result);
    			return 0;
   diff --git a/Zend/zend_vm_def.h b/Zend/zend_vm_def.h
   index 3c3065e1568..4e4a7cfdf78 100644
   --- a/Zend/zend_vm_def.h
   +++ b/Zend/zend_vm_def.h
   @@ -6278,7 +6278,11 @@ ZEND_VM_C_LABEL(num_index):
    		} else if ((OP2_TYPE & (IS_VAR|IS_CV)) && EXPECTED(Z_TYPE_P(offset) == IS_REFERENCE)) {
    			offset = Z_REFVAL_P(offset);
    			ZEND_VM_C_GOTO(add_again);
   -		} else if (Z_TYPE_P(offset) == IS_NULL) {
   +		} else if (UNEXPECTED(Z_TYPE_P(offset) == IS_NULL)) {
   +			zend_error(E_DEPRECATED, "Using null as an array offset is deprecated, use an empty string instead");
   +			if (UNEXPECTED(EG(exception))) {
   +				HANDLE_EXCEPTION();
   +			}
    			str = ZSTR_EMPTY_ALLOC();
    			ZEND_VM_C_GOTO(str_index);
    		} else if (Z_TYPE_P(offset) == IS_DOUBLE) {
   diff --git a/Zend/zend_vm_execute.h b/Zend/zend_vm_execute.h
   index 50870ce463d..fc8735de516 100644
   Binary files a/Zend/zend_vm_execute.h and b/Zend/zend_vm_execute.h differ
   
4. ndossche

   added

   Category: Engine

   Status: Verified

   and removed

   Status: Needs Triage

   on Oct 18, 2025
5. Girgias

   linked a pull request that will close this issueFix GH-20194: null offset deprecation not emitted for writes #20238on Oct 20, 2025
6. Girgias

   closed this as completedin 9a1b8a7on Oct 29, 2025
7. Girgias

   added a commit that references this issue on Oct 29, 2025

   Merge branch 'PHP-8.5'

   ...

   This issue will close once commit 0df31e5 is merged into the 'master' branch.

   0df31e5
8. thomas-0816 commented on Oct 29, 2025

   

   thomas-0816

   on Oct 29, 2025

   Author

   More actions

   Thank You!
9. justin-oh commented on Sep 22, 2026

   

   justin-oh

   on Sep 22, 2026

   Last edited by justin-oh

   More actions

   I can get why $array[null => 'value']; can be deprecated but why $a[null]?

   PHP is full of code like this:

   $keyThatMightBeNull;
   
   $arrayWithKeys;
   
   $value = $arrayWithKeys[$keyThatMightBeNull] ?? null;

   You should handle $a[null] the same way you would handle $a['key_that_doesnt_exist']. Otherwise, 1000s of people each have to go and update dozens of lines of code to be like this:

   $keyThatMightBeNull;
   
   $arrayWithKeys;
   
   $value = null;
   
   if (null !== $keyThatMightBeNull) {
       $value = $arrayWithKeys[$keyThatMightBeNull] ?? null;
   }

   It seems so unnecessary when it can be handled directly in the source code intuitively.

   Further, the "use an empty string instead" part of the error message is misleading in the case of trying to access $a[null]. The error is suggesting they try accessing $a[''] which could also not exist or provide an incorrect value in that context.
10. justin-oh commented on Sep 22, 2026

    

    justin-oh

    on Sep 22, 2026

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    Basically I would expect these scenarios:

    1. $array[$nonNullKeyThatDoesntExist] and $array[$nullKeyThatDoesntExist] behave the same; this is intuitive
    2. $array[$nonNullKeyThatExists] functions as usual
    3. $array[$nullKeyThatExists] functions as usual; only show deprecation for $array[null => 'value'] and in a future version of PHP throw an error for $array[null => 'value']; when the developer is forced to remove their null key, point 1 handles $array[$nullKeyThatDoesntExist]