If the first numeric index of an array is negative let the next one stay negative

Zend/zend_compile.c

@@ -7048,7 +7048,9 @@ static zend_bool zend_try_ct_eval_array(zval *result, zend_ast *ast) /* {{{ */
 					break;
 			}
 		} else {
-			if (!zend_hash_next_index_insert(Z_ARRVAL_P(result), value)) {
+			/* Bail out of CT eval in case the deprecation notice would be emitted so it may be handled in RT */
+			if (HASH_ADD_NEXT_EMITS_DEPRECATED(Z_ARRVAL_P(result)) ||
+				!zend_hash_next_index_insert(Z_ARRVAL_P(result), value)) {
 				zval_ptr_dtor_nogc(value);
 				zval_ptr_dtor(result);
 				return 0;

Zend/zend_hash.c

@@ -181,7 +181,7 @@ static zend_always_inline void _zend_hash_init_int(HashTable *ht, uint32_t nSize
 	ht->nNumUsed = 0;
 	ht->nNumOfElements = 0;
 	ht->nInternalPointer = HT_INVALID_IDX;
-	ht->nNextFreeElement = 0;
+	ht->nNextFreeElement = ZEND_LONG_MIN;
 	ht->pDestructor = pDestructor;
 	ht->nTableSize = zend_hash_check_size(nSize);
 }
@@ -789,6 +789,18 @@ static zend_always_inline zval *_zend_hash_index_add_or_update_i(HashTable *ht,
 	IS_CONSISTENT(ht);
 	HT_ASSERT_RC1(ht);
 
+	/* Removing this block will end the deprecation phase and allow the new behavior */
+	if (UNEXPECTED(flag & HASH_ADD_NEXT
+		&& HASH_ADD_NEXT_EMITS_DEPRECATED(ht))) {
+		zend_error(E_DEPRECATED, "In the next major version of PHP the implicit keys of this array will start from " ZEND_LONG_FMT " instead of 0",
+			ht->nNextFreeElement);
+		h = 0;
+	}
+
+	if (h == ZEND_LONG_MIN && flag & HASH_ADD_NEXT) {
+		h = 0;
+	}
+
 	if (UNEXPECTED(!(HT_FLAGS(ht) & HASH_FLAG_INITIALIZED))) {
 		CHECK_INIT(ht, h < ht->nTableSize);
 		if (h < ht->nTableSize) {
@@ -841,7 +853,7 @@ static zend_always_inline zval *_zend_hash_index_add_or_update_i(HashTable *ht,
 		}
 		zend_hash_iterators_update(ht, HT_INVALID_IDX, h);
 		if ((zend_long)h >= (zend_long)ht->nNextFreeElement) {
-			ht->nNextFreeElement = h < ZEND_LONG_MAX ? h + 1 : ZEND_LONG_MAX;
+			ht->nNextFreeElement = (zend_long)h < ZEND_LONG_MAX ? h + 1 : ZEND_LONG_MAX;
 		}
 		p->h = h;
 		p->key = NULL;
@@ -863,7 +875,7 @@ static zend_always_inline zval *_zend_hash_index_add_or_update_i(HashTable *ht,
 			}
 			ZVAL_COPY_VALUE(&p->val, pData);
 			if ((zend_long)h >= (zend_long)ht->nNextFreeElement) {
-				ht->nNextFreeElement = h < ZEND_LONG_MAX ? h + 1 : ZEND_LONG_MAX;
+				ht->nNextFreeElement = (zend_long)h < ZEND_LONG_MAX ? h + 1 : ZEND_LONG_MAX;
 			}
 			return &p->val;
 		}
@@ -879,7 +891,7 @@ static zend_always_inline zval *_zend_hash_index_add_or_update_i(HashTable *ht,
 	}
 	zend_hash_iterators_update(ht, HT_INVALID_IDX, idx);
 	if ((zend_long)h >= (zend_long)ht->nNextFreeElement) {
-		ht->nNextFreeElement = h < ZEND_LONG_MAX ? h + 1 : ZEND_LONG_MAX;
+		ht->nNextFreeElement = (zend_long)h < ZEND_LONG_MAX ? h + 1 : ZEND_LONG_MAX;
 	}
 	p = ht->arData + idx;
 	p->h = h;
@@ -1471,7 +1483,7 @@ ZEND_API void ZEND_FASTCALL zend_hash_clean(HashTable *ht)
 	}
 	ht->nNumUsed = 0;
 	ht->nNumOfElements = 0;
-	ht->nNextFreeElement = 0;
+	ht->nNextFreeElement = ZEND_LONG_MIN;
 	ht->nInternalPointer = HT_INVALID_IDX;
 }
 
@@ -1510,7 +1522,7 @@ ZEND_API void ZEND_FASTCALL zend_symtable_clean(HashTable *ht)
 	}
 	ht->nNumUsed = 0;
 	ht->nNumOfElements = 0;
-	ht->nNextFreeElement = 0;
+	ht->nNextFreeElement = ZEND_LONG_MIN;
 	ht->nInternalPointer = HT_INVALID_IDX;
 }
 
@@ -1837,7 +1849,7 @@ ZEND_API HashTable* ZEND_FASTCALL zend_array_dup(HashTable *source)
 		target->nTableMask = HT_MIN_MASK;
 		target->nNumUsed = 0;
 		target->nNumOfElements = 0;
-		target->nNextFreeElement = 0;
+		target->nNextFreeElement = ZEND_LONG_MIN;
 		target->nInternalPointer = HT_INVALID_IDX;
 		HT_SET_DATA_ADDR(target, &uninitialized_bucket);
 	} else if (GC_FLAGS(source) & IS_ARRAY_IMMUTABLE) {

Zend/zend_hash.h

@@ -35,6 +35,9 @@
 #define HASH_ADD_NEW			(1<<3)
 #define HASH_ADD_NEXT			(1<<4)
 
+#define HASH_ADD_NEXT_EMITS_DEPRECATED(ht) \
+	((ht)->nNextFreeElement > ZEND_LONG_MIN && (ht)->nNextFreeElement < 0)
+
 #define HASH_FLAG_CONSISTENCY      ((1<<0) | (1<<1))
 #define HASH_FLAG_PACKED           (1<<2)
 #define HASH_FLAG_INITIALIZED      (1<<3)

ext/opcache/Optimizer/sccp.c

@@ -475,7 +475,7 @@ static inline int ct_eval_del_array_elem(zval *result, zval *key) {
 static inline int ct_eval_add_array_elem(zval *result, zval *value, zval *key) {
 	if (!key) {
 		SEPARATE_ARRAY(result);
-		if ((value = zend_hash_next_index_insert(Z_ARR_P(result), value))) {
+		if (!HASH_ADD_NEXT_EMITS_DEPRECATED(Z_ARR_P(result)) && (value = zend_hash_next_index_insert(Z_ARR_P(result), value))) {
 			Z_TRY_ADDREF_P(value);
 			return SUCCESS;
 		}

ext/standard/array.c

@@ -3275,7 +3275,7 @@ PHP_FUNCTION(array_pop)
 	ZVAL_DEREF(val);
 	ZVAL_COPY(return_value, val);
 
-	if (!p->key && Z_ARRVAL_P(stack)->nNextFreeElement > 0 && p->h >= (zend_ulong)(Z_ARRVAL_P(stack)->nNextFreeElement - 1)) {
+	if (!p->key && p->h >= (zend_ulong)(Z_ARRVAL_P(stack)->nNextFreeElement - 1)) {
 		Z_ARRVAL_P(stack)->nNextFreeElement = Z_ARRVAL_P(stack)->nNextFreeElement - 1;
 	}
 

ext/standard/tests/array/array_fill_variation1.phpt

@@ -117,6 +117,8 @@ array(2) {
   int(100)
 }
 -- Iteration 2 --
+
+Deprecated: In the next major version of PHP the implicit keys of this array will start from -9 instead of 0 in %s
 array(2) {
   [-10]=>
   int(100)

ext/standard/tests/array/array_fill_variation1_64bit.phpt

@@ -117,6 +117,8 @@ array(2) {
   int(100)
 }
 -- Iteration 2 --
+
+Deprecated: In the next major version of PHP the implicit keys of this array will start from -9 instead of 0 in %s
 array(2) {
   [-10]=>
   int(100)

ext/standard/tests/array/bug67693.phpt

@@ -14,7 +14,8 @@ var_dump($array);
 
 echo"\nDone";
 ?>
---EXPECT--
+--EXPECTF--
+Deprecated: In the next major version of PHP the implicit keys of this array will start from -1 instead of 0 in %s
 array(2) {
   [0]=>
   int(0)

ext/standard/tests/array/count_recursive.phpt

@@ -161,6 +161,8 @@ COUNT_NORMAL: should be 3, is 3
 COUNT_RECURSIVE: should be 13, is 13
 
 *** Testing possible variations of count() function on arrays ***
+Deprecated: In the next major version of PHP the implicit keys of this array will start from -1 instead of 0 in %s
+
 -- Iteration 0 --
 COUNT_NORMAL is 0
 COUNT_RECURSIVE is 0

main/php_variables.c

@@ -245,6 +245,10 @@ PHPAPI void php_register_variable_ex(char *var_name, zval *val, zval *track_vars
 	} else {
 plain_var:
 		if (!index) {
+			/* Avoid the deprecation notice during globals registration */
+			if (HASH_ADD_NEXT_EMITS_DEPRECATED(symtable1)) {
+				symtable1->nNextFreeElement = 0;
+			}
 			if (zend_hash_next_index_insert(symtable1, val) == NULL) {
 				zval_ptr_dtor(val);
 			}