diff --git a/.phpcs.xml.dist b/.phpcs.xml.dist
new file mode 100644
index 00000000..3eafb6ca
--- /dev/null
+++ b/.phpcs.xml.dist
@@ -0,0 +1,22 @@
+<?xml version="1.0"?>
+<ruleset xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" name="PHP_CodeSniffer"
+         xsi:noNamespaceSchemaLocation="vendor/squizlabs/php_codesniffer/phpcs.xsd">
+
+    <file>samples</file>
+    <file>src</file>
+    <file>tests</file>
+
+    <exclude-pattern>samples/Header.php</exclude-pattern>
+    <exclude-pattern>*/tests/Core/*/*Test\.(inc|css|js)$</exclude-pattern>
+
+    <arg name="report-width" value="200"/>
+    <arg name="parallel" value="80"/>
+    <arg name="cache" value="/tmp/.phpspreadsheet.phpcs-cache"/>
+    <arg name="colors"/>
+    <arg value="np"/>
+
+    <!-- Include the whole PSR12 standard -->
+    <rule ref="PSR12">
+        <exclude name="PSR2.Methods.MethodDeclaration.Underscore"/>
+    </rule>
+</ruleset>
diff --git a/composer.json b/composer.json
index 32df7bac..00b6fe9e 100644
--- a/composer.json
+++ b/composer.json
@@ -28,7 +28,7 @@
     "scripts": {
         "check": [
             "php-cs-fixer fix --ansi --dry-run --diff",
-            "phpcs --report-width=200 samples/ src/ tests/ --ignore=samples/Header.php --standard=PSR12 -n",
+            "phpcs",
             "phpunit --color=always"
         ],
         "fix": [
diff --git a/src/PhpSpreadsheet/Calculation/Calculation.php b/src/PhpSpreadsheet/Calculation/Calculation.php
index 19e2fc89..10ba064a 100644
--- a/src/PhpSpreadsheet/Calculation/Calculation.php
+++ b/src/PhpSpreadsheet/Calculation/Calculation.php
@@ -3277,7 +3277,7 @@ class Calculation
         }
 
         //    Parse the formula and return the token stack
-        return $this->_parseFormula($formula);
+        return $this->internalParseFormula($formula);
     }
 
     /**
@@ -3418,7 +3418,7 @@ class Calculation
 
         //    Parse the formula onto the token stack and calculate the value
         $this->cyclicReferenceStack->push($wsCellReference);
-        $cellValue = $this->processTokenStack($this->_parseFormula($formula, $pCell), $cellID, $pCell);
+        $cellValue = $this->processTokenStack($this->internalParseFormula($formula, $pCell), $cellID, $pCell);
         $this->cyclicReferenceStack->pop();
 
         // Save to calculation cache
@@ -3765,7 +3765,7 @@ class Calculation
      *
      * @return bool
      */
-    private function _parseFormula($formula, ?Cell $pCell = null)
+    private function internalParseFormula($formula, ?Cell $pCell = null)
     {
         if (($formula = $this->convertMatrixReferences(trim($formula))) === false) {
             return false;