Make constant redeclaration a warning

We missed the change to make this an Error exception in PHP 8,
but at least elevate it to a warning, to avoid a notice -> exception
jump at a later time.

Author: nikic

Zend/tests/008.phpt

@@ -32,13 +32,13 @@ echo "Done\n";
 --EXPECTF--
 TypeError: define(): Argument #1 ($constant_name) must be of type string, array given
 
-Notice: Constant TRUE already defined in %s on line %d
+Warning: Constant TRUE already defined in %s on line %d
 bool(false)
 bool(true)
 bool(true)
 bool(true)
 
-Notice: Constant test const already defined in %s on line %d
+Warning: Constant test const already defined in %s on line %d
 bool(false)
 bool(true)
 bool(true)

Zend/tests/bug53305.phpt

@@ -14,6 +14,6 @@ var_dump(constant('__COMPILER_HALT_OFFSET__1'.chr(0)));
 
 ?>
 --EXPECTF--
-Notice: Constant __COMPILER_HALT_OFFSET__ already defined in %s on line %d
+Warning: Constant __COMPILER_HALT_OFFSET__ already defined in %s on line %d
 int(1)
 int(4)

Zend/tests/constants_001.phpt

@@ -17,7 +17,7 @@ var_dump(constant('1foo'));
 
 ?>
 --EXPECTF--
-Notice: Constant 1 already defined in %s on line %d
+Warning: Constant 1 already defined in %s on line %d
 int(2)
 int(2)
 int(2)

Zend/tests/constants_004.phpt

@@ -10,4 +10,4 @@ const foo = 2;
 
 ?>
 --EXPECTF--
-Notice: Constant foo\foo already defined in %s on line %d
+Warning: Constant foo\foo already defined in %s on line %d

Zend/tests/constants_008.phpt

@@ -13,5 +13,5 @@ if (defined('a')) {
 
 ?>
 --EXPECTF--
-Notice: Constant a already defined in %s on line %d
+Warning: Constant a already defined in %s on line %d
 2

Zend/tests/halt_compiler3.phpt

@@ -5,4 +5,4 @@ __HALT_COMPILER(); bad define() of __COMPILER_HALT_OFFSET__ 1
 define ('__COMPILER_HALT_OFFSET__', 1);
 ?>
 --EXPECTF--
-Notice: Constant __COMPILER_HALT_OFFSET__ already defined in %s on line %d
+Warning: Constant __COMPILER_HALT_OFFSET__ already defined in %s on line %d

Zend/tests/halt_compiler4.phpt

@@ -7,4 +7,4 @@ __HALT_COMPILER();
 ?>
 ==DONE==
 --EXPECTF--
-Notice: Constant __COMPILER_HALT_OFFSET__ already defined in %s on line %d
+Warning: Constant __COMPILER_HALT_OFFSET__ already defined in %s on line %d

Zend/zend_constants.c

@@ -503,7 +503,7 @@ ZEND_API zend_result zend_register_constant(zend_constant *c)
 		|| (!persistent && zend_get_special_const(ZSTR_VAL(name), ZSTR_LEN(name)))
 		|| zend_hash_add_constant(EG(zend_constants), name, c) == NULL
 	) {
-		zend_error(E_NOTICE,"Constant %s already defined", ZSTR_VAL(name));
+		zend_error(E_WARNING, "Constant %s already defined", ZSTR_VAL(name));
 		zend_string_release(c->name);
 		if (!persistent) {
 			zval_ptr_dtor_nogc(&c->value);

ext/opcache/tests/bug71127.phpt

@@ -21,5 +21,5 @@ include($file);
 @unlink(__DIR__ . "/bug71127.inc");
 ?>
 --EXPECTF--
-Notice: Constant FOO already defined in %sbug71127.inc on line %d
+Warning: Constant FOO already defined in %sbug71127.inc on line %d
 okey