diff --git a/ext/standard/array.c b/ext/standard/array.c
index a2fef8b145283..735b8f9165e54 100644
--- a/ext/standard/array.c
+++ b/ext/standard/array.c
@@ -4866,7 +4866,7 @@ PHP_FUNCTION(array_change_key_case)
 	zend_string *string_key;
 	zend_string *new_key;
 	zend_ulong num_key;
-	zend_long change_to_upper=0;
+	zend_long change_to_upper = PHP_CASE_LOWER;
 
 	ZEND_PARSE_PARAMETERS_START(1, 2)
 		Z_PARAM_ARRAY(array)
@@ -4874,13 +4874,18 @@ PHP_FUNCTION(array_change_key_case)
 		Z_PARAM_LONG(change_to_upper)
 	ZEND_PARSE_PARAMETERS_END();
 
+	if (change_to_upper != PHP_CASE_LOWER && change_to_upper != PHP_CASE_UPPER) {
+		zend_argument_value_error(2, "must be either CASE_LOWER or CASE_UPPER");
+		RETURN_THROWS();
+	}
+
 	array_init_size(return_value, zend_hash_num_elements(Z_ARRVAL_P(array)));
 
 	ZEND_HASH_FOREACH_KEY_VAL(Z_ARRVAL_P(array), num_key, string_key, entry) {
 		if (!string_key) {
 			entry = zend_hash_index_update(Z_ARRVAL_P(return_value), num_key, entry);
 		} else {
-			if (change_to_upper) {
+			if (change_to_upper == PHP_CASE_UPPER) {
 				new_key = zend_string_toupper(string_key);
 			} else {
 				new_key = zend_string_tolower(string_key);
diff --git a/ext/standard/tests/array/array_change_key_case_flag_error.phpt b/ext/standard/tests/array/array_change_key_case_flag_error.phpt
new file mode 100644
index 0000000000000..e83a21815c990
--- /dev/null
+++ b/ext/standard/tests/array/array_change_key_case_flag_error.phpt
@@ -0,0 +1,14 @@
+--TEST--
+array_change_key_case(): invalid $case argument
+--FILE--
+<?php
+
+try {
+    array_change_key_case([], -10);
+} catch (Throwable $e) {
+    echo $e::class, ': ', $e->getMessage(), PHP_EOL;
+}
+
+?>
+--EXPECT--
+ValueError: array_change_key_case(): Argument #2 ($case) must be either CASE_LOWER or CASE_UPPER
diff --git a/ext/standard/tests/array/array_change_key_case_variation.phpt b/ext/standard/tests/array/array_change_key_case_variation.phpt
deleted file mode 100644
index c221a3f34101a..0000000000000
--- a/ext/standard/tests/array/array_change_key_case_variation.phpt
+++ /dev/null
@@ -1,50 +0,0 @@
---TEST--
-Test array_change_key_case() function - 2
---FILE--
-<?php
-
-$item = array ("one" => 1, "two" => 2, "THREE" => 3, "FOUR" => "four");
-
-/* use 'case' argument other than CASE_LOWER & CASE_UPPER */
-try {
-    var_dump(array_change_key_case($item, "CASE_UPPER"));
-} catch (TypeError $e) {
-    echo $e->getMessage(), "\n";
-}
-var_dump(array_change_key_case($item, 5));
-
-/* when keys are different in terms of only case */
-/* should return one value key pair with key being in lowercase */
-var_dump( array_change_key_case( array("ONE" => 1, "one" => 3, "One" => 4) ) );
-
-/* should return one value key pair with key being in uppercase */
-var_dump( array_change_key_case( array("ONE" => 1, "one" => 2, "One" => 3), CASE_UPPER ) );
-var_dump( array_change_key_case( array("ONE" => 1, "one" => 1, "One" => 2), 5 ) );
-
-echo "end\n";
-?>
---EXPECT--
-array_change_key_case(): Argument #2 ($case) must be of type int, string given
-array(4) {
-  ["ONE"]=>
-  int(1)
-  ["TWO"]=>
-  int(2)
-  ["THREE"]=>
-  int(3)
-  ["FOUR"]=>
-  string(4) "four"
-}
-array(1) {
-  ["one"]=>
-  int(4)
-}
-array(1) {
-  ["ONE"]=>
-  int(3)
-}
-array(1) {
-  ["ONE"]=>
-  int(2)
-}
-end
diff --git a/ext/standard/tests/array/array_change_key_case_variation4.phpt b/ext/standard/tests/array/array_change_key_case_variation4.phpt
deleted file mode 100644
index 82d211451638a..0000000000000
--- a/ext/standard/tests/array/array_change_key_case_variation4.phpt
+++ /dev/null
@@ -1,132 +0,0 @@
---TEST--
-Test array_change_key_case() function : usage variations - different int values for $case
---FILE--
-<?php
-/*
- * Pass different integer values as $case argument to array_change_key_case() to test behaviour
- */
-
-echo "*** Testing array_change_key_case() : usage variations ***\n";
-
-$input = array('One' => 'un', 'TWO' => 'deux', 'three' => 'trois');
-for ($i = -5; $i <=5; $i += 1){
-    echo "\n-- \$sort argument is $i --\n";
-    $temp = $input;
-    var_dump(array_change_key_case($temp, $i));
-}
-
-echo "Done";
-?>
---EXPECT--
-*** Testing array_change_key_case() : usage variations ***
-
--- $sort argument is -5 --
-array(3) {
-  ["ONE"]=>
-  string(2) "un"
-  ["TWO"]=>
-  string(4) "deux"
-  ["THREE"]=>
-  string(5) "trois"
-}
-
--- $sort argument is -4 --
-array(3) {
-  ["ONE"]=>
-  string(2) "un"
-  ["TWO"]=>
-  string(4) "deux"
-  ["THREE"]=>
-  string(5) "trois"
-}
-
--- $sort argument is -3 --
-array(3) {
-  ["ONE"]=>
-  string(2) "un"
-  ["TWO"]=>
-  string(4) "deux"
-  ["THREE"]=>
-  string(5) "trois"
-}
-
--- $sort argument is -2 --
-array(3) {
-  ["ONE"]=>
-  string(2) "un"
-  ["TWO"]=>
-  string(4) "deux"
-  ["THREE"]=>
-  string(5) "trois"
-}
-
--- $sort argument is -1 --
-array(3) {
-  ["ONE"]=>
-  string(2) "un"
-  ["TWO"]=>
-  string(4) "deux"
-  ["THREE"]=>
-  string(5) "trois"
-}
-
--- $sort argument is 0 --
-array(3) {
-  ["one"]=>
-  string(2) "un"
-  ["two"]=>
-  string(4) "deux"
-  ["three"]=>
-  string(5) "trois"
-}
-
--- $sort argument is 1 --
-array(3) {
-  ["ONE"]=>
-  string(2) "un"
-  ["TWO"]=>
-  string(4) "deux"
-  ["THREE"]=>
-  string(5) "trois"
-}
-
--- $sort argument is 2 --
-array(3) {
-  ["ONE"]=>
-  string(2) "un"
-  ["TWO"]=>
-  string(4) "deux"
-  ["THREE"]=>
-  string(5) "trois"
-}
-
--- $sort argument is 3 --
-array(3) {
-  ["ONE"]=>
-  string(2) "un"
-  ["TWO"]=>
-  string(4) "deux"
-  ["THREE"]=>
-  string(5) "trois"
-}
-
--- $sort argument is 4 --
-array(3) {
-  ["ONE"]=>
-  string(2) "un"
-  ["TWO"]=>
-  string(4) "deux"
-  ["THREE"]=>
-  string(5) "trois"
-}
-
--- $sort argument is 5 --
-array(3) {
-  ["ONE"]=>
-  string(2) "un"
-  ["TWO"]=>
-  string(4) "deux"
-  ["THREE"]=>
-  string(5) "trois"
-}
-Done