diff --git a/CHANGELOG.md b/CHANGELOG.md
index a2fd0cc1..7f07303a 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -25,7 +25,7 @@ and this project adheres to [Semantic Versioning](https://semver.org).
 
 ### Fixed
 
-- Nothing
+- Fully flatten an array [Issue #2955](https://github.com/PHPOffice/PhpSpreadsheet/issues/2955) [PR #2956](https://github.com/PHPOffice/PhpSpreadsheet/pull/2956)
 
 ## 1.24.1 - 2022-07-18
 
diff --git a/src/PhpSpreadsheet/Calculation/Functions.php b/src/PhpSpreadsheet/Calculation/Functions.php
index ddd3e200..b3d6998c 100644
--- a/src/PhpSpreadsheet/Calculation/Functions.php
+++ b/src/PhpSpreadsheet/Calculation/Functions.php
@@ -573,24 +573,20 @@ class Functions
             return (array) $array;
         }
 
-        $arrayValues = [];
-        foreach ($array as $value) {
+        $flattened = [];
+        $stack = array_values($array);
+
+        while ($stack) {
+            $value = array_shift($stack);
+
             if (is_array($value)) {
-                foreach ($value as $val) {
-                    if (is_array($val)) {
-                        foreach ($val as $v) {
-                            $arrayValues[] = $v;
-                        }
-                    } else {
-                        $arrayValues[] = $val;
-                    }
-                }
+                array_unshift($stack, ...array_values($value));
             } else {
-                $arrayValues[] = $value;
+                $flattened[] = $value;
             }
         }
 
-        return $arrayValues;
+        return $flattened;
     }
 
     /**
diff --git a/tests/PhpSpreadsheetTests/Calculation/ArrayTest.php b/tests/PhpSpreadsheetTests/Calculation/ArrayTest.php
new file mode 100644
index 00000000..60c336cf
--- /dev/null
+++ b/tests/PhpSpreadsheetTests/Calculation/ArrayTest.php
@@ -0,0 +1,34 @@
+<?php
+
+namespace PhpOffice\PhpSpreadsheetTests\Calculation;
+
+use PhpOffice\PhpSpreadsheet\Calculation\Functions;
+use PHPUnit\Framework\TestCase;
+
+class ArrayTest extends TestCase
+{
+    public function testMultiDimensionalArrayIsFlattened(): void
+    {
+        $array = [
+            0 => [
+                0 => [
+                    32 => [
+                        'B' => 'PHP',
+                    ],
+                ],
+            ],
+            1 => [
+                0 => [
+                    32 => [
+                        'C' => 'Spreadsheet',
+                    ],
+                ],
+            ],
+        ];
+
+        $values = Functions::flattenArray($array);
+
+        self::assertIsNotArray($values[0]);
+        self::assertIsNotArray($values[1]);
+    }
+}
diff --git a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ConcatenateTest.php b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ConcatenateTest.php
index 6c9a871d..31fb94fa 100644
--- a/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ConcatenateTest.php
+++ b/tests/PhpSpreadsheetTests/Calculation/Functions/TextData/ConcatenateTest.php
@@ -2,6 +2,8 @@
 
 namespace PhpOffice\PhpSpreadsheetTests\Calculation\Functions\TextData;
 
+use PhpOffice\PhpSpreadsheet\Spreadsheet;
+
 class ConcatenateTest extends AllSetupTeardown
 {
     /**
@@ -30,4 +32,27 @@ class ConcatenateTest extends AllSetupTeardown
     {
         return require 'tests/data/Calculation/TextData/CONCATENATE.php';
     }
+
+    public function testConcatenateWithIndexMatch(): void
+    {
+        $spreadsheet = new Spreadsheet();
+        $sheet1 = $spreadsheet->getActiveSheet();
+        $sheet1->setTitle('Formula');
+        $sheet1->fromArray(
+            [
+                ['Number', 'Formula'],
+                ['52101293', '=CONCAT(INDEX(Lookup!$B$2, MATCH($A2, Lookup!$A$2, 0)))'],
+            ]
+        );
+        $sheet2 = $spreadsheet->createSheet();
+        $sheet2->setTitle('Lookup');
+        $sheet2->fromArray(
+            [
+                ['Lookup', 'Match'],
+                ['52101293', 'PHP'],
+            ]
+        );
+        self::assertSame('PHP', $sheet1->getCell('B2')->getCalculatedValue());
+        $spreadsheet->disconnectWorksheets();
+    }
 }