diff --git a/ext/standard/dir.c b/ext/standard/dir.c
index 7c1f8efe68875..e8ea1620e4741 100644
--- a/ext/standard/dir.c
+++ b/ext/standard/dir.c
@@ -537,6 +537,11 @@ PHP_FUNCTION(scandir)
 		Z_PARAM_RESOURCE_OR_NULL(zcontext)
 	ZEND_PARSE_PARAMETERS_END();
 
+	if (flags != PHP_SCANDIR_SORT_ASCENDING && flags != PHP_SCANDIR_SORT_NONE) {
+		zend_argument_value_error(2, "must be one of PHP_SCANDIR_SORT_ASCENDING, or SCANDIR_SORT_NONE");
+		RETURN_THROWS();
+	}
+
 	if (dirn_len < 1) {
 		zend_argument_must_not_be_empty_error(1);
 		RETURN_THROWS();
diff --git a/ext/standard/tests/dir/scandir_basic-win32-mb.phpt b/ext/standard/tests/dir/scandir_basic-win32-mb.phpt
index 87e6e7e6dac86..c1b8b06b4bbc0 100644
--- a/ext/standard/tests/dir/scandir_basic-win32-mb.phpt
+++ b/ext/standard/tests/dir/scandir_basic-win32-mb.phpt
@@ -28,7 +28,11 @@ var_dump(scandir($directory));
 echo "\n-- scandir() with all arguments --\n";
 $sorting_order = SCANDIR_SORT_DESCENDING;
 $context = stream_context_create();
-var_dump(scandir($directory, $sorting_order, $context));
+try {
+  var_dump(scandir($directory, $sorting_order, $context));
+} catch (ValueError $e) {
+    echo $e->getMessage();
+}
 
 delete_files($directory, 3, "私はガラスを食べられますfile");
 ?>
@@ -55,15 +59,4 @@ array(5) {
 }
 
 -- scandir() with all arguments --
-array(5) {
-  [0]=>
-  string(45) "私はガラスを食べられますfile3.tmp"
-  [1]=>
-  string(45) "私はガラスを食べられますfile2.tmp"
-  [2]=>
-  string(45) "私はガラスを食べられますfile1.tmp"
-  [3]=>
-  string(2) ".."
-  [4]=>
-  string(1) "."
-}
+scandir(): Argument #2 ($sorting_order) must be one of PHP_SCANDIR_SORT_ASCENDING, or SCANDIR_SORT_NONE
diff --git a/ext/standard/tests/dir/scandir_basic.phpt b/ext/standard/tests/dir/scandir_basic.phpt
index d86aa291421d2..7c3446c0d4bed 100644
--- a/ext/standard/tests/dir/scandir_basic.phpt
+++ b/ext/standard/tests/dir/scandir_basic.phpt
@@ -22,8 +22,11 @@ var_dump(scandir($directory));
 echo "\n-- scandir() with all arguments --\n";
 $sorting_order = SCANDIR_SORT_DESCENDING;
 $context = stream_context_create();
-var_dump(scandir($directory, $sorting_order, $context));
-
+try {
+  var_dump(scandir($directory, $sorting_order, $context));
+} catch (ValueError $e) {
+    echo $e->getMessage();
+}
 delete_files($directory, 3);
 ?>
 --CLEAN--
@@ -49,15 +52,4 @@ array(5) {
 }
 
 -- scandir() with all arguments --
-array(5) {
-  [0]=>
-  string(9) "file3.tmp"
-  [1]=>
-  string(9) "file2.tmp"
-  [2]=>
-  string(9) "file1.tmp"
-  [3]=>
-  string(2) ".."
-  [4]=>
-  string(1) "."
-}
+scandir(): Argument #2 ($sorting_order) must be one of PHP_SCANDIR_SORT_ASCENDING, or SCANDIR_SORT_NONE
diff --git a/ext/standard/tests/dir/scandir_invalid_flag.phpt b/ext/standard/tests/dir/scandir_invalid_flag.phpt
new file mode 100644
index 0000000000000..d53fdaa675e5b
--- /dev/null
+++ b/ext/standard/tests/dir/scandir_invalid_flag.phpt
@@ -0,0 +1,39 @@
+--TEST--
+scandir() flag validation and behavior
+--FILE--
+<?php
+
+echo "== Valid flags ==\n";
+
+$valid_flags = [
+    SCANDIR_SORT_ASCENDING,
+    SCANDIR_SORT_NONE,
+];
+
+foreach ($valid_flags as $flag) {
+    $result = scandir(__DIR__, $flag);
+    echo is_array($result) ? "OK\n" : "FAIL\n";
+}
+
+echo "== Invalid flags ==\n";
+
+$invalid_flags = [-1, 3, 999, PHP_INT_MAX];
+
+foreach ($invalid_flags as $flag) {
+    try {
+        scandir(__DIR__, $flag);
+    } catch (ValueError $e) {
+        echo $e->getMessage() . PHP_EOL;
+    }
+}
+
+?>
+--EXPECT--
+== Valid flags ==
+OK
+OK
+== Invalid flags ==
+scandir(): Argument #2 ($sorting_order) must be one of PHP_SCANDIR_SORT_ASCENDING, or SCANDIR_SORT_NONE
+scandir(): Argument #2 ($sorting_order) must be one of PHP_SCANDIR_SORT_ASCENDING, or SCANDIR_SORT_NONE
+scandir(): Argument #2 ($sorting_order) must be one of PHP_SCANDIR_SORT_ASCENDING, or SCANDIR_SORT_NONE
+scandir(): Argument #2 ($sorting_order) must be one of PHP_SCANDIR_SORT_ASCENDING, or SCANDIR_SORT_NONE
diff --git a/ext/standard/tests/dir/scandir_variation10-win32-mb.phpt b/ext/standard/tests/dir/scandir_variation10-win32-mb.phpt
index 69f55bc53b226..4fd46b680c3f1 100644
--- a/ext/standard/tests/dir/scandir_variation10-win32-mb.phpt
+++ b/ext/standard/tests/dir/scandir_variation10-win32-mb.phpt
@@ -28,8 +28,12 @@ mkdir($dir);
 @create_files($dir, 2, "numeric", 0755, 1, "w", "私はガラスを食べられますfile");
 
 // Deterministic tests.
-var_dump(scandir($dir, SCANDIR_SORT_ASCENDING));
-var_dump(scandir($dir, SCANDIR_SORT_DESCENDING));
+try {
+  var_dump(scandir($dir, SCANDIR_SORT_ASCENDING));
+  var_dump(scandir($dir, SCANDIR_SORT_DESCENDING));
+} catch (ValueError $e) {
+    echo $e->getMessage();
+}
 
 // Non-deterministic tests.
 $files = scandir($dir, SCANDIR_SORT_NONE);
@@ -61,17 +65,7 @@ array(4) {
   [3]=>
   string(45) "私はガラスを食べられますfile2.tmp"
 }
-array(4) {
-  [0]=>
-  string(45) "私はガラスを食べられますfile2.tmp"
-  [1]=>
-  string(45) "私はガラスを食べられますfile1.tmp"
-  [2]=>
-  string(2) ".."
-  [3]=>
-  string(1) "."
-}
-int(4)
+scandir(): Argument #2 ($sorting_order) must be one of PHP_SCANDIR_SORT_ASCENDING, or SCANDIR_SORT_NONEint(4)
 bool(true)
 bool(true)
 bool(true)
diff --git a/ext/standard/tests/dir/scandir_variation10.phpt b/ext/standard/tests/dir/scandir_variation10.phpt
index 35df3c3e7565e..37023c2027fe9 100644
--- a/ext/standard/tests/dir/scandir_variation10.phpt
+++ b/ext/standard/tests/dir/scandir_variation10.phpt
@@ -22,8 +22,12 @@ mkdir($dir);
 @create_files($dir, 2);
 
 // Deterministic tests.
-var_dump(scandir($dir, SCANDIR_SORT_ASCENDING));
-var_dump(scandir($dir, SCANDIR_SORT_DESCENDING));
+try {
+  var_dump(scandir($dir, SCANDIR_SORT_ASCENDING));
+  var_dump(scandir($dir, SCANDIR_SORT_DESCENDING));
+} catch (ValueError $e) {
+    echo $e->getMessage();
+}
 
 // Non-deterministic tests.
 $files = scandir($dir, SCANDIR_SORT_NONE);
@@ -55,17 +59,7 @@ array(4) {
   [3]=>
   string(9) "file2.tmp"
 }
-array(4) {
-  [0]=>
-  string(9) "file2.tmp"
-  [1]=>
-  string(9) "file1.tmp"
-  [2]=>
-  string(2) ".."
-  [3]=>
-  string(1) "."
-}
-int(4)
+scandir(): Argument #2 ($sorting_order) must be one of PHP_SCANDIR_SORT_ASCENDING, or SCANDIR_SORT_NONEint(4)
 bool(true)
 bool(true)
 bool(true)
diff --git a/ext/standard/tests/dir/scandir_variation9-win32-mb.phpt b/ext/standard/tests/dir/scandir_variation9-win32-mb.phpt
index 44d8b6daa5f9e..bc6a519c59f40 100644
--- a/ext/standard/tests/dir/scandir_variation9-win32-mb.phpt
+++ b/ext/standard/tests/dir/scandir_variation9-win32-mb.phpt
@@ -27,7 +27,11 @@ mkdir($dir);
 $ints = array (PHP_INT_MAX, -PHP_INT_MAX, 0);
 
 foreach($ints as $sorting_order) {
+  try {
     var_dump( scandir($dir, $sorting_order) );
+  } catch (ValueError $e) {
+    echo $e->getMessage() . PHP_EOL;
+  }
 }
 
 delete_files($dir, 2, "私はガラスを食べられますfile");
@@ -39,26 +43,8 @@ rmdir($dir);
 ?>
 --EXPECT--
 *** Testing scandir() : usage variations ***
-array(4) {
-  [0]=>
-  string(45) "私はガラスを食べられますfile2.tmp"
-  [1]=>
-  string(45) "私はガラスを食べられますfile1.tmp"
-  [2]=>
-  string(2) ".."
-  [3]=>
-  string(1) "."
-}
-array(4) {
-  [0]=>
-  string(45) "私はガラスを食べられますfile2.tmp"
-  [1]=>
-  string(45) "私はガラスを食べられますfile1.tmp"
-  [2]=>
-  string(2) ".."
-  [3]=>
-  string(1) "."
-}
+scandir(): Argument #2 ($sorting_order) must be one of PHP_SCANDIR_SORT_ASCENDING, or SCANDIR_SORT_NONE
+scandir(): Argument #2 ($sorting_order) must be one of PHP_SCANDIR_SORT_ASCENDING, or SCANDIR_SORT_NONE
 array(4) {
   [0]=>
   string(1) "."
diff --git a/ext/standard/tests/dir/scandir_variation9.phpt b/ext/standard/tests/dir/scandir_variation9.phpt
index 56e5575e55904..1daaa5e2bdca4 100644
--- a/ext/standard/tests/dir/scandir_variation9.phpt
+++ b/ext/standard/tests/dir/scandir_variation9.phpt
@@ -21,7 +21,11 @@ mkdir($dir);
 $ints = array (PHP_INT_MAX, -PHP_INT_MAX, 0);
 
 foreach($ints as $sorting_order) {
-    var_dump( scandir($dir, $sorting_order) );
+  try {
+     var_dump( scandir($dir, $sorting_order) );
+  } catch (ValueError $e) {
+    echo $e->getMessage() . PHP_EOL;
+  }
 }
 
 delete_files($dir, 2);
@@ -31,28 +35,10 @@ delete_files($dir, 2);
 $dir = __DIR__ . '/scandir_variation9';
 rmdir($dir);
 ?>
---EXPECT--
+--EXPECTF--
 *** Testing scandir() : usage variations ***
-array(4) {
-  [0]=>
-  string(9) "file2.tmp"
-  [1]=>
-  string(9) "file1.tmp"
-  [2]=>
-  string(2) ".."
-  [3]=>
-  string(1) "."
-}
-array(4) {
-  [0]=>
-  string(9) "file2.tmp"
-  [1]=>
-  string(9) "file1.tmp"
-  [2]=>
-  string(2) ".."
-  [3]=>
-  string(1) "."
-}
+scandir(): Argument #2 ($sorting_order) must be one of PHP_SCANDIR_SORT_ASCENDING, or SCANDIR_SORT_NONE
+scandir(): Argument #2 ($sorting_order) must be one of PHP_SCANDIR_SORT_ASCENDING, or SCANDIR_SORT_NONE
 array(4) {
   [0]=>
   string(1) "."