diff --git a/src/OutputFormat.php b/src/OutputFormat.php
index 7f3786be..4498b34b 100644
--- a/src/OutputFormat.php
+++ b/src/OutputFormat.php
@@ -39,7 +39,8 @@ class OutputFormat
      * Spacing
      * Note that these strings are not sanity-checked: the value should only consist of whitespace
      * Any newline character will be indented according to the current level.
-     * The triples (After, Before, Between) can be set using a wildcard (e.g. `$oFormat->set('Space*Rules', "\n");`)
+     * The triples (After, Before, Between) can be set using a wildcard
+     * (e.g. `$outputFormat->set('Space*Rules', "\n");`)
      *
      * @var string
      *
@@ -217,7 +218,7 @@ class OutputFormat
     /**
      * @var OutputFormatter|null
      */
-    private $oFormatter;
+    private $outputFormatter;
 
     /**
      * @var OutputFormat|null
@@ -788,7 +789,7 @@ public function nextLevel(): self
         if ($this->oNextLevelFormat === null) {
             $this->oNextLevelFormat = clone $this;
             $this->oNextLevelFormat->iIndentationLevel++;
-            $this->oNextLevelFormat->oFormatter = null;
+            $this->oNextLevelFormat->outputFormatter = null;
         }
         return $this->oNextLevelFormat;
     }
@@ -800,10 +801,10 @@ public function beLenient(): void
 
     public function getFormatter(): OutputFormatter
     {
-        if ($this->oFormatter === null) {
-            $this->oFormatter = new OutputFormatter($this);
+        if ($this->outputFormatter === null) {
+            $this->outputFormatter = new OutputFormatter($this);
         }
-        return $this->oFormatter;
+        return $this->outputFormatter;
     }
 
     /**
diff --git a/src/OutputFormatter.php b/src/OutputFormatter.php
index 48db2e0b..e7f2af64 100644
--- a/src/OutputFormatter.php
+++ b/src/OutputFormatter.php
@@ -12,11 +12,11 @@ class OutputFormatter
     /**
      * @var OutputFormat
      */
-    private $oFormat;
+    private $outputFormat;
 
-    public function __construct(OutputFormat $oFormat)
+    public function __construct(OutputFormat $outputFormat)
     {
-        $this->oFormat = $oFormat;
+        $this->outputFormat = $outputFormat;
     }
 
     /**
@@ -25,7 +25,7 @@ public function __construct(OutputFormat $oFormat)
      */
     public function space($sName, $sType = null): string
     {
-        $sSpaceString = $this->oFormat->get("Space$sName");
+        $sSpaceString = $this->outputFormat->get("Space$sName");
         // If $sSpaceString is an array, we have multiple values configured
         // depending on the type of object the space applies to
         if (\is_array($sSpaceString)) {
@@ -91,7 +91,7 @@ public function spaceAfterSelectorSeparator(): string
      */
     public function spaceBeforeListArgumentSeparator($sSeparator): string
     {
-        $spaceForSeparator = $this->oFormat->getSpaceBeforeListArgumentSeparators();
+        $spaceForSeparator = $this->outputFormat->getSpaceBeforeListArgumentSeparators();
 
         return $spaceForSeparator[$sSeparator] ?? $this->space('BeforeListArgumentSeparator', $sSeparator);
     }
@@ -101,7 +101,7 @@ public function spaceBeforeListArgumentSeparator($sSeparator): string
      */
     public function spaceAfterListArgumentSeparator($sSeparator): string
     {
-        $spaceForSeparator = $this->oFormat->getSpaceAfterListArgumentSeparators();
+        $spaceForSeparator = $this->outputFormat->getSpaceAfterListArgumentSeparators();
 
         return $spaceForSeparator[$sSeparator] ?? $this->space('AfterListArgumentSeparator', $sSeparator);
     }
@@ -120,7 +120,7 @@ public function spaceBeforeOpeningBrace(): string
      */
     public function safely($cCode)
     {
-        if ($this->oFormat->get('IgnoreExceptions')) {
+        if ($this->outputFormat->get('IgnoreExceptions')) {
             // If output exceptions are ignored, run the code with exception guards
             try {
                 return $cCode();
@@ -142,9 +142,9 @@ public function safely($cCode)
     public function implode(string $sSeparator, array $aValues, $bIncreaseLevel = false): string
     {
         $result = '';
-        $oFormat = $this->oFormat;
+        $outputFormat = $this->outputFormat;
         if ($bIncreaseLevel) {
-            $oFormat = $oFormat->nextLevel();
+            $outputFormat = $outputFormat->nextLevel();
         }
         $bIsFirst = true;
         foreach ($aValues as $mValue) {
@@ -154,7 +154,7 @@ public function implode(string $sSeparator, array $aValues, $bIncreaseLevel = fa
                 $result .= $sSeparator;
             }
             if ($mValue instanceof Renderable) {
-                $result .= $mValue->render($oFormat);
+                $result .= $mValue->render($outputFormat);
             } else {
                 $result .= $mValue;
             }
@@ -169,7 +169,7 @@ public function implode(string $sSeparator, array $aValues, $bIncreaseLevel = fa
      */
     public function removeLastSemicolon($sString)
     {
-        if ($this->oFormat->get('SemicolonAfterLastRule')) {
+        if ($this->outputFormat->get('SemicolonAfterLastRule')) {
             return $sString;
         }
         $sString = \explode(';', $sString);
@@ -184,7 +184,7 @@ public function removeLastSemicolon($sString)
 
     public function comments(Commentable $oCommentable): string
     {
-        if (!$this->oFormat->bRenderComments) {
+        if (!$this->outputFormat->bRenderComments) {
             return '';
         }
 
@@ -193,7 +193,7 @@ public function comments(Commentable $oCommentable): string
         $iLastCommentIndex = \count($comments) - 1;
 
         foreach ($comments as $i => $oComment) {
-            $result .= $oComment->render($this->oFormat);
+            $result .= $oComment->render($this->outputFormat);
             $result .= $i === $iLastCommentIndex ? $this->spaceAfterBlocks() : $this->spaceBetweenBlocks();
         }
         return $result;
@@ -212,6 +212,6 @@ private function prepareSpace($sSpaceString): string
      */
     private function indent(): string
     {
-        return \str_repeat($this->oFormat->sIndentation, $this->oFormat->getIndentationLevel());
+        return \str_repeat($this->outputFormat->sIndentation, $this->outputFormat->getIndentationLevel());
     }
 }