Fix PHP 8.3 and 8.4 compatibility

- Swap handler init order: call zend_object_std_init before setting
  custom handlers, as PHP 8.3 overwrites the handlers pointer during init
- Rename Override test class to CustomNumber to avoid PHP 8.3 reserved name
- Add explicit nullable type syntax for PHP 8.4 deprecation warnings

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

Author: rudi-augment

src/decimal.c

@@ -68,8 +68,8 @@ static php_decimal_t *php_decimal_alloc()
 
     // TODO we should still go through everything to check for branch prediction.
     if (obj) {
-        obj->std.handlers = &php_decimal_handlers;
         zend_object_std_init((zend_object *) obj, php_decimal_decimal_ce);
+        obj->std.handlers = &php_decimal_handlers;
     } else {
         php_decimal_memory_error();
     }

src/rational.c

@@ -69,8 +69,8 @@ static php_rational_t *php_decimal_rational_alloc()
     php_rational_t *obj = ecalloc(1, sizeof(php_rational_t));
 
     if (EXPECTED(obj)) {
-        obj->std.handlers = &php_decimal_rational_handlers;
         zend_object_std_init((zend_object *) obj, php_decimal_rational_ce);
+        obj->std.handlers = &php_decimal_rational_handlers;
     } else {
         php_decimal_memory_error();
     }

tests/Number/helpers/Number.php

@@ -84,12 +84,12 @@ public function shiftr($places): \Decimal\Number
         return new static($this->value / (10 ** $places));
     }
 
-    public function round(int $places = NULL, int $mode = NULL): \Decimal\Number
+    public function round(?int $places = NULL, ?int $mode = NULL): \Decimal\Number
     {
         return new static($this->toDecimal(\Decimal\Decimal::MAX_PRECISION)->round($places, $mode)->toString());
     }
 
-    public function toFixed(int $places = NULL, bool $commas = NULL, int $mode = NULL): string
+    public function toFixed(?int $places = NULL, ?bool $commas = NULL, ?int $mode = NULL): string
     {
         return new static($this->toDecimal(\Decimal\Decimal::MAX_PRECISION)->toFixed($places, $commas, $mode));
     }

tests/Number/json.phpt

@@ -9,15 +9,15 @@ var_dump(json_encode(Number::valueOf("0.3")));
 /**
  * Test that we can override the internal alias.
  */
-class Override extends Number
+class CustomNumber extends Number
 {
     public function jsonSerialize(): string
     {
         return "*";
     }
 }
 
-var_dump(json_encode(Override::valueOf(5)));
+var_dump(json_encode(CustomNumber::valueOf(5)));
 
 ?>
 --EXPECT--