Fix GH-9905: constant() behaves inconsistent when class is undefined

Directly referring to a constant of an undefined throws an exception;
there is not much point in `constant()` raising a fatal error in this
case.

Closes GH-9907.

NEWS

@@ -2,6 +2,9 @@ PHP                                                                        NEWS
 |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
 ?? ??? ????, PHP 8.1.14
 
+- Core:
+  . Fixed bug GH-9905 (constant() behaves inconsistent when class is undefined).
+    (cmb)
 
 24 Nov 2022, PHP 8.1.13
 

ext/standard/basic_functions.c

@@ -589,7 +589,7 @@ PHP_FUNCTION(constant)
 	ZEND_PARSE_PARAMETERS_END();
 
 	scope = zend_get_executed_scope();
-	c = zend_get_constant_ex(const_name, scope, 0);
+	c = zend_get_constant_ex(const_name, scope, ZEND_FETCH_CLASS_EXCEPTION);
 	if (!c) {
 		RETURN_THROWS();
 	}

ext/standard/tests/general_functions/gh9905.phpt

@@ -0,0 +1,12 @@
+--TEST--
+GH-9905 (constant() behaves inconsistent when class is undefined)
+--FILE--
+<?php
+try {
+    \constant("\NonExistantClass::non_existant_constant");
+} catch (\Throwable|\Error|\Exception $e) {
+    echo($e->getMessage());
+}
+?>
+--EXPECT--
+Class "NonExistantClass" not found

tests/lang/bug44827.phpt

@@ -21,5 +21,4 @@ try {
 ?>
 --EXPECTF--
 define(): Argument #1 ($constant_name) cannot be a class constant
-
+Class "" not found
-Fatal error: Class "" not found in %s on line %d