Declare arguments as required when they are

Closes #110

src/PhpSpreadsheet/Cell.php

@@ -118,7 +118,7 @@ class Cell
      *
      * @throws Exception
      */
-    public function __construct($pValue = null, $pDataType = null, Worksheet $pSheet = null)
+    public function __construct($pValue, $pDataType, Worksheet $pSheet)
     {
         // Initialise cell value
         $this->value = $pValue;
@@ -990,12 +990,8 @@ class Cell
      *
      * @throws Exception
      */
-    public static function setValueBinder(Cell\IValueBinder $binder = null)
+    public static function setValueBinder(Cell\IValueBinder $binder)
     {
-        if ($binder === null) {
-            throw new Exception('A \\PhpOffice\\PhpSpreadsheet\\Cell\\IValueBinder is required for PhpSpreadsheet to function correctly.');
-        }
-
         self::$valueBinder = $binder;
     }
 

src/PhpSpreadsheet/Chart/Legend.php

@@ -73,8 +73,9 @@ class Legend
     /**
      * Create a new Legend.
      *
-     * @param mixed $position
+     * @param string $position
-     * @param mixed $overlay
+     * @param Layout|null $layout
+     * @param bool $overlay
      */
     public function __construct($position = self::POSITION_RIGHT, Layout $layout = null, $overlay = false)
     {

src/PhpSpreadsheet/Chart/PlotArea.php

@@ -43,7 +43,8 @@ class PlotArea
     /**
      * Create a new PlotArea.
      *
-     * @param mixed $plotSeries
+     * @param Layout|null $layout
+     * @param array $plotSeries
      */
     public function __construct(Layout $layout = null, array $plotSeries = [])
     {

src/PhpSpreadsheet/Chart/Title.php

@@ -44,6 +44,7 @@ class Title
      * Create a new Title.
      *
      * @param null|mixed $caption
+     * @param null|Layout $layout
      */
     public function __construct($caption = null, Layout $layout = null)
     {

src/PhpSpreadsheet/HashTable.php

@@ -81,7 +81,7 @@ class HashTable
      *
      * @throws Exception
      */
-    public function add(IComparable $pSource = null)
+    public function add(IComparable $pSource)
     {
         $hash = $pSource->getHashCode();
         if (!isset($this->items[$hash])) {
@@ -97,7 +97,7 @@ class HashTable
      *
      * @throws Exception
      */
-    public function remove(IComparable $pSource = null)
+    public function remove(IComparable $pSource)
     {
         $hash = $pSource->getHashCode();
         if (isset($this->items[$hash])) {

src/PhpSpreadsheet/NamedRange.php

@@ -238,7 +238,7 @@ class NamedRange
      *
      * @return NamedRange
      */
-    public static function resolveRange($pNamedRange, Worksheet $pSheet = null)
+    public static function resolveRange($pNamedRange, Worksheet $pSheet)
     {
         return $pSheet->getParent()->getNamedRange($pNamedRange, $pSheet);
     }

src/PhpSpreadsheet/ReferenceHelper.php

@@ -384,7 +384,7 @@ class ReferenceHelper
      *
      * @throws Exception
      */
-    public function insertNewBefore($pBefore = 'A1', $pNumCols = 0, $pNumRows = 0, Worksheet $pSheet = null)
+    public function insertNewBefore($pBefore, $pNumCols, $pNumRows, Worksheet $pSheet)
     {
         $remove = ($pNumCols < 0 || $pNumRows < 0);
         $allCoordinates = $pSheet->getCoordinates();

src/PhpSpreadsheet/RichText.php

@@ -68,7 +68,7 @@ class RichText implements IComparable
      *
      * @return RichText
      */
-    public function addText(RichText\ITextElement $pText = null)
+    public function addText(RichText\ITextElement $pText)
     {
         $this->richTextElements[] = $pText;
 

src/PhpSpreadsheet/Shared/Date.php

@@ -251,7 +251,7 @@ class Date
      *
      * @return float MS Excel serialized date/time value
      */
-    public static function dateTimeToExcel(\DateTimeInterface $dateValue = null)
+    public static function dateTimeToExcel(\DateTimeInterface $dateValue)
     {
         return self::formattedPHPToExcel(
             $dateValue->format('Y'),

src/PhpSpreadsheet/Shared/Font.php

@@ -330,7 +330,7 @@ class Font
      *
      * @return int Text width in pixels (no padding added)
      */
-    public static function getTextWidthPixelsApprox($columnText, \PhpOffice\PhpSpreadsheet\Style\Font $font = null, $rotation = 0)
+    public static function getTextWidthPixelsApprox($columnText, \PhpOffice\PhpSpreadsheet\Style\Font $font, $rotation = 0)
     {
         $fontName = $font->getName();
         $fontSize = $font->getSize();

src/PhpSpreadsheet/Style/Border.php

@@ -256,7 +256,7 @@ class Border extends Supervisor implements \PhpOffice\PhpSpreadsheet\IComparable
      *
      * @return Border
      */
-    public function setColor(Color $pValue = null)
+    public function setColor(Color $pValue)
     {
         // make sure parameter is a real color and not a supervisor
         $color = $pValue->getIsSupervisor() ? $pValue->getSharedComponent() : $pValue;

src/PhpSpreadsheet/Style/Fill.php

@@ -264,7 +264,7 @@ class Fill extends Supervisor implements \PhpOffice\PhpSpreadsheet\IComparable
      *
      * @return Fill
      */
-    public function setStartColor(Color $pValue = null)
+    public function setStartColor(Color $pValue)
     {
         // make sure parameter is a real color and not a supervisor
         $color = $pValue->getIsSupervisor() ? $pValue->getSharedComponent() : $pValue;
@@ -298,7 +298,7 @@ class Fill extends Supervisor implements \PhpOffice\PhpSpreadsheet\IComparable
      *
      * @return Fill
      */
-    public function setEndColor(Color $pValue = null)
+    public function setEndColor(Color $pValue)
     {
         // make sure parameter is a real color and not a supervisor
         $color = $pValue->getIsSupervisor() ? $pValue->getSharedComponent() : $pValue;

src/PhpSpreadsheet/Style/Font.php

@@ -528,7 +528,7 @@ class Font extends Supervisor implements \PhpOffice\PhpSpreadsheet\IComparable
      *
      * @return Font
      */
-    public function setColor(Color $pValue = null)
+    public function setColor(Color $pValue)
     {
         // make sure parameter is a real color and not a supervisor
         $color = $pValue->getIsSupervisor() ? $pValue->getSharedComponent() : $pValue;

src/PhpSpreadsheet/Worksheet.php

@@ -550,7 +550,7 @@ class Worksheet implements IComparable
      *
      * @return Chart
      */
-    public function addChart(Chart $pChart = null, $iChartIndex = null)
+    public function addChart(Chart $pChart, $iChartIndex = null)
     {
         $pChart->setWorksheet($this);
         if (is_null($iChartIndex)) {
@@ -1546,7 +1546,7 @@ class Worksheet implements IComparable
      *
      * @return Worksheet
      */
-    public function duplicateStyle(Style $pCellStyle = null, $pRange = '')
+    public function duplicateStyle(Style $pCellStyle, $pRange)
     {
         // make sure we have a real style and not supervisor
         $style = $pCellStyle->getIsSupervisor() ? $pCellStyle->getSharedComponent() : $pCellStyle;
@@ -1594,7 +1594,7 @@ class Worksheet implements IComparable
      *
      * @return Worksheet
      */
-    public function duplicateConditionalStyle(array $pCellStyle = null, $pRange = '')
+    public function duplicateConditionalStyle(array $pCellStyle, $pRange = '')
     {
         foreach ($pCellStyle as $cellStyle) {
             if (!($cellStyle instanceof Style\Conditional)) {

src/PhpSpreadsheet/Worksheet/HeaderFooter.php

@@ -428,7 +428,7 @@ class HeaderFooter
      *
      * @return HeaderFooter
      */
-    public function addImage(HeaderFooterDrawing $image = null, $location = self::IMAGE_HEADER_LEFT)
+    public function addImage(HeaderFooterDrawing $image, $location = self::IMAGE_HEADER_LEFT)
     {
         $this->headerFooterImages[$location] = $image;
 

src/PhpSpreadsheet/Writer/Ods.php

@@ -48,7 +48,7 @@ class Ods extends BaseWriter implements IWriter
      *
      * @param \PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet
      */
-    public function __construct(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null)
+    public function __construct(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet)
     {
         $this->setSpreadsheet($spreadsheet);
 
@@ -183,7 +183,7 @@ class Ods extends BaseWriter implements IWriter
      *
      * @return self
      */
-    public function setSpreadsheet(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null)
+    public function setSpreadsheet(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet)
     {
         $this->spreadSheet = $spreadsheet;
 

src/PhpSpreadsheet/Writer/Xls/Font.php

@@ -45,7 +45,7 @@ class Font
      *
      * @param \PhpOffice\PhpSpreadsheet\Style\Font $font
      */
-    public function __construct(\PhpOffice\PhpSpreadsheet\Style\Font $font = null)
+    public function __construct(\PhpOffice\PhpSpreadsheet\Style\Font $font)
     {
         $this->colorIndex = 0x7FFF;
         $this->font = $font;

src/PhpSpreadsheet/Writer/Xls/Xf.php

@@ -136,7 +136,7 @@ class Xf
      *
      * @param \PhpOffice\PhpSpreadsheet\Style The XF format
      */
-    public function __construct(\PhpOffice\PhpSpreadsheet\Style $style = null)
+    public function __construct(\PhpOffice\PhpSpreadsheet\Style $style)
     {
         $this->isStyleXf = false;
         $this->fontIndex = 0;

src/PhpSpreadsheet/Writer/Xlsx.php

@@ -111,7 +111,7 @@ class Xlsx extends BaseWriter implements IWriter
      *
      * @param \PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet
      */
-    public function __construct(\PhpOffice\PhpSpreadsheet\Spreadsheet $spreadsheet = null)
+    public function __construct(\PhpOffice\PhpSpreadsheet\Spreadsheet $spreadsheet)
     {
         // Assign PhpSpreadsheet
         $this->setSpreadsheet($spreadsheet);
@@ -411,7 +411,7 @@ class Xlsx extends BaseWriter implements IWriter
      *
      * @return Xlsx
      */
-    public function setSpreadsheet(Spreadsheet $spreadsheet = null)
+    public function setSpreadsheet(Spreadsheet $spreadsheet)
     {
         $this->spreadSheet = $spreadsheet;
 

src/PhpSpreadsheet/Writer/Xlsx/Chart.php

@@ -47,7 +47,7 @@ class Chart extends WriterPart
      *
      * @return string XML Output
      */
-    public function writeChart(\PhpOffice\PhpSpreadsheet\Chart $pChart = null, $calculateCellValues = true)
+    public function writeChart(\PhpOffice\PhpSpreadsheet\Chart $pChart, $calculateCellValues = true)
     {
         $this->calculateCellValues = $calculateCellValues;
 
@@ -358,7 +358,7 @@ class Chart extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeDataLabels($objWriter, Layout $chartLayout = null)
+    private function writeDataLabels(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, Layout $chartLayout = null)
     {
         $objWriter->startElement('c:dLbls');
 

src/PhpSpreadsheet/Writer/Xlsx/Comments.php

@@ -35,7 +35,7 @@ class Comments extends WriterPart
      *
      * @return string XML Output
      */
-    public function writeComments(\PhpOffice\PhpSpreadsheet\Worksheet $pWorksheet = null)
+    public function writeComments(\PhpOffice\PhpSpreadsheet\Worksheet $pWorksheet)
     {
         // Create XML writer
         $objWriter = null;
@@ -94,7 +94,7 @@ class Comments extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeComment(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, $pCellReference = 'A1', \PhpOffice\PhpSpreadsheet\Comment $pComment = null, $pAuthors = null)
+    private function writeComment(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, $pCellReference, \PhpOffice\PhpSpreadsheet\Comment $pComment, array $pAuthors)
     {
         // comment
         $objWriter->startElement('comment');
@@ -118,7 +118,7 @@ class Comments extends WriterPart
      *
      * @return string XML Output
      */
-    public function writeVMLComments(\PhpOffice\PhpSpreadsheet\Worksheet $pWorksheet = null)
+    public function writeVMLComments(\PhpOffice\PhpSpreadsheet\Worksheet $pWorksheet)
     {
         // Create XML writer
         $objWriter = null;
@@ -187,12 +187,12 @@ class Comments extends WriterPart
      * Write VML comment to XML format.
      *
      * @param \PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter XML Writer
-     * @param string $pCellReference Cell reference
+     * @param string $pCellReference Cell reference, eg: 'A1'
      * @param \PhpOffice\PhpSpreadsheet\Comment $pComment Comment
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeVMLComment(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, $pCellReference = 'A1', \PhpOffice\PhpSpreadsheet\Comment $pComment = null)
+    private function writeVMLComment(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, $pCellReference, \PhpOffice\PhpSpreadsheet\Comment $pComment)
     {
         // Metadata
         list($column, $row) = \PhpOffice\PhpSpreadsheet\Cell::coordinateFromString($pCellReference);

src/PhpSpreadsheet/Writer/Xlsx/ContentTypes.php

@@ -36,7 +36,7 @@ class ContentTypes extends WriterPart
      *
      * @return string XML Output
      */
-    public function writeContentTypes(\PhpOffice\PhpSpreadsheet\Spreadsheet $spreadsheet = null, $includeCharts = false)
+    public function writeContentTypes(\PhpOffice\PhpSpreadsheet\Spreadsheet $spreadsheet, $includeCharts = false)
     {
         // Create XML writer
         $objWriter = null;

src/PhpSpreadsheet/Writer/Xlsx/DocProps.php

@@ -35,7 +35,7 @@ class DocProps extends WriterPart
      *
      * @return string XML Output
      */
-    public function writeDocPropsApp(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null)
+    public function writeDocPropsApp(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet)
     {
         // Create XML writer
         $objWriter = null;
@@ -134,7 +134,7 @@ class DocProps extends WriterPart
      *
      * @return string XML Output
      */
-    public function writeDocPropsCore(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null)
+    public function writeDocPropsCore(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet)
     {
         // Create XML writer
         $objWriter = null;
@@ -203,7 +203,7 @@ class DocProps extends WriterPart
      *
      * @return string XML Output
      */
-    public function writeDocPropsCustom(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null)
+    public function writeDocPropsCustom(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet)
     {
         $customPropertyList = $spreadsheet->getProperties()->getCustomProperties();
         if (empty($customPropertyList)) {

src/PhpSpreadsheet/Writer/Xlsx/Drawing.php

@@ -90,7 +90,7 @@ class Drawing extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    public function writeChart(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Chart $pChart = null, $pRelationId = -1)
+    public function writeChart(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Chart $pChart, $pRelationId = -1)
     {
         $tl = $pChart->getTopLeftPosition();
         $tl['colRow'] = \PhpOffice\PhpSpreadsheet\Cell::coordinateFromString($tl['cell']);
@@ -293,7 +293,7 @@ class Drawing extends WriterPart
      *
      * @return string XML Output
      */
-    public function writeVMLHeaderFooterImages(\PhpOffice\PhpSpreadsheet\Worksheet $pWorksheet = null)
+    public function writeVMLHeaderFooterImages(\PhpOffice\PhpSpreadsheet\Worksheet $pWorksheet)
     {
         // Create XML writer
         $objWriter = null;
@@ -442,7 +442,7 @@ class Drawing extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeVMLHeaderFooterImage(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, $pReference = '', \PhpOffice\PhpSpreadsheet\Worksheet\HeaderFooterDrawing $pImage = null)
+    private function writeVMLHeaderFooterImage(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, $pReference, \PhpOffice\PhpSpreadsheet\Worksheet\HeaderFooterDrawing $pImage)
     {
         // Calculate object id
         preg_match('{(\d+)}', md5($pReference), $m);
@@ -485,7 +485,7 @@ class Drawing extends WriterPart
      *
      * @return \PhpOffice\PhpSpreadsheet\Worksheet\Drawing[] All drawings in PhpSpreadsheet
      */
-    public function allDrawings(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null)
+    public function allDrawings(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet)
     {
         // Get an array of all drawings
         $aDrawings = [];

src/PhpSpreadsheet/Writer/Xlsx/Rels.php

@@ -35,7 +35,7 @@ class Rels extends WriterPart
      *
      * @return string XML Output
      */
-    public function writeRelationships(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null)
+    public function writeRelationships(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet)
     {
         // Create XML writer
         $objWriter = null;
@@ -110,7 +110,7 @@ class Rels extends WriterPart
      *
      * @return string XML Output
      */
-    public function writeWorkbookRelationships(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null)
+    public function writeWorkbookRelationships(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet)
     {
         // Create XML writer
         $objWriter = null;
@@ -193,7 +193,7 @@ class Rels extends WriterPart
      *
      * @return string XML Output
      */
-    public function writeWorksheetRelationships(\PhpOffice\PhpSpreadsheet\Worksheet $pWorksheet = null, $pWorksheetId = 1, $includeCharts = false)
+    public function writeWorksheetRelationships(\PhpOffice\PhpSpreadsheet\Worksheet $pWorksheet, $pWorksheetId = 1, $includeCharts = false)
     {
         // Create XML writer
         $objWriter = null;
@@ -353,7 +353,7 @@ class Rels extends WriterPart
      *
      * @return string XML Output
      */
-    public function writeHeaderFooterDrawingRelationships(\PhpOffice\PhpSpreadsheet\Worksheet $pWorksheet = null)
+    public function writeHeaderFooterDrawingRelationships(\PhpOffice\PhpSpreadsheet\Worksheet $pWorksheet)
     {
         // Create XML writer
         $objWriter = null;

src/PhpSpreadsheet/Writer/Xlsx/RelsRibbon.php

@@ -35,7 +35,7 @@ class RelsRibbon extends WriterPart
      *
      * @return string XML Output
      */
-    public function writeRibbonRelationships(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null)
+    public function writeRibbonRelationships(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet)
     {
         // Create XML writer
         $objWriter = null;

src/PhpSpreadsheet/Writer/Xlsx/RelsVBA.php

@@ -35,7 +35,7 @@ class RelsVBA extends WriterPart
      *
      * @return string XML Output
      */
-    public function writeVBARelationships(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null)
+    public function writeVBARelationships(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet)
     {
         // Create XML writer
         $objWriter = null;

src/PhpSpreadsheet/Writer/Xlsx/StringTable.php

@@ -85,9 +85,8 @@ class StringTable extends WriterPart
      *
      * @return string XML Output
      */
-    public function writeStringTable(array $pStringTable = null)
+    public function writeStringTable(array $pStringTable)
     {
-        if ($pStringTable !== null) {
         // Create XML writer
         $objWriter = null;
         if ($this->getParentWriter()->getUseDiskCaching()) {
@@ -127,8 +126,6 @@ class StringTable extends WriterPart
 
         return $objWriter->getData();
     }
-        throw new \PhpOffice\PhpSpreadsheet\Writer\Exception('Invalid string table array passed.');
-    }
 
     /**
      * Write Rich Text.
@@ -139,7 +136,7 @@ class StringTable extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    public function writeRichText(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\RichText $pRichText = null, $prefix = null)
+    public function writeRichText(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\RichText $pRichText, $prefix = null)
     {
         if ($prefix !== null) {
             $prefix .= ':';
@@ -224,7 +221,7 @@ class StringTable extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    public function writeRichTextForCharts(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, $pRichText = null, $prefix = null)
+    public function writeRichTextForCharts(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, $pRichText = null, $prefix = null)
     {
         if (!$pRichText instanceof \PhpOffice\PhpSpreadsheet\RichText) {
             $textRun = $pRichText;

src/PhpSpreadsheet/Writer/Xlsx/Style.php

@@ -35,7 +35,7 @@ class Style extends WriterPart
      *
      * @return string XML Output
      */
-    public function writeStyles(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null)
+    public function writeStyles(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet)
     {
         // Create XML writer
         $objWriter = null;
@@ -166,7 +166,7 @@ class Style extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeFill(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Style\Fill $pFill = null)
+    private function writeFill(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Style\Fill $pFill)
     {
         // Check if this is a pattern type or gradient type
         if ($pFill->getFillType() === \PhpOffice\PhpSpreadsheet\Style\Fill::FILL_GRADIENT_LINEAR ||
@@ -187,7 +187,7 @@ class Style extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeGradientFill(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Style\Fill $pFill = null)
+    private function writeGradientFill(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Style\Fill $pFill)
     {
         // fill
         $objWriter->startElement('fill');
@@ -232,7 +232,7 @@ class Style extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writePatternFill(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Style\Fill $pFill = null)
+    private function writePatternFill(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Style\Fill $pFill)
     {
         // fill
         $objWriter->startElement('fill');
@@ -271,7 +271,7 @@ class Style extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeFont(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Style\Font $pFont = null)
+    private function writeFont(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Style\Font $pFont)
     {
         // font
         $objWriter->startElement('font');
@@ -352,7 +352,7 @@ class Style extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeBorder(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Style\Borders $pBorders = null)
+    private function writeBorder(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Style\Borders $pBorders)
     {
         // Write border
         $objWriter->startElement('border');
@@ -390,7 +390,7 @@ class Style extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeCellStyleXf(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Style $pStyle = null, \PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null)
+    private function writeCellStyleXf(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Style $pStyle, \PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet)
     {
         // xf
         $objWriter->startElement('xf');
@@ -466,7 +466,7 @@ class Style extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeCellStyleDxf(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Style $pStyle = null)
+    private function writeCellStyleDxf(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Style $pStyle)
     {
         // dxf
         $objWriter->startElement('dxf');
@@ -532,7 +532,7 @@ class Style extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeBorderPr(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, $pName = 'left', \PhpOffice\PhpSpreadsheet\Style\Border $pBorder = null)
+    private function writeBorderPr(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, $pName, \PhpOffice\PhpSpreadsheet\Style\Border $pBorder)
     {
         // Write BorderPr
         if ($pBorder->getBorderStyle() != \PhpOffice\PhpSpreadsheet\Style\Border::BORDER_NONE) {
@@ -557,7 +557,7 @@ class Style extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeNumFmt(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Style\NumberFormat $pNumberFormat = null, $pId = 0)
+    private function writeNumFmt(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Style\NumberFormat $pNumberFormat, $pId = 0)
     {
         // Translate formatcode
         $formatCode = $pNumberFormat->getFormatCode();
@@ -580,7 +580,7 @@ class Style extends WriterPart
      *
      * @return \PhpOffice\PhpSpreadsheet\Style[] All styles in PhpSpreadsheet
      */
-    public function allStyles(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null)
+    public function allStyles(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet)
     {
         return $spreadsheet->getCellXfCollection();
     }
@@ -594,7 +594,7 @@ class Style extends WriterPart
      *
      * @return \PhpOffice\PhpSpreadsheet\Style\Conditional[] All conditional styles in PhpSpreadsheet
      */
-    public function allConditionalStyles(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null)
+    public function allConditionalStyles(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet)
     {
         // Get an array of all styles
         $aStyles = [];
@@ -620,7 +620,7 @@ class Style extends WriterPart
      *
      * @return \PhpOffice\PhpSpreadsheet\Style\Fill[] All fills in PhpSpreadsheet
      */
-    public function allFills(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null)
+    public function allFills(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet)
     {
         // Get an array of unique fills
         $aFills = [];
@@ -654,7 +654,7 @@ class Style extends WriterPart
      *
      * @return \PhpOffice\PhpSpreadsheet\Style\Font[] All fonts in PhpSpreadsheet
      */
-    public function allFonts(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null)
+    public function allFonts(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet)
     {
         // Get an array of unique fonts
         $aFonts = [];
@@ -679,7 +679,7 @@ class Style extends WriterPart
      *
      * @return \PhpOffice\PhpSpreadsheet\Style\Borders[] All borders in PhpSpreadsheet
      */
-    public function allBorders(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null)
+    public function allBorders(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet)
     {
         // Get an array of unique borders
         $aBorders = [];
@@ -704,7 +704,7 @@ class Style extends WriterPart
      *
      * @return \PhpOffice\PhpSpreadsheet\Style\NumberFormat[] All number formats in PhpSpreadsheet
      */
-    public function allNumberFormats(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null)
+    public function allNumberFormats(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet)
     {
         // Get an array of unique number formats
         $aNumFmts = [];

src/PhpSpreadsheet/Writer/Xlsx/Theme.php

@@ -137,7 +137,7 @@ class Theme extends WriterPart
      *
      * @return string XML Output
      */
-    public function writeTheme(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null)
+    public function writeTheme(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet)
     {
         // Create XML writer
         $objWriter = null;

src/PhpSpreadsheet/Writer/Xlsx/Workbook.php

@@ -36,7 +36,7 @@ class Workbook extends WriterPart
      *
      * @return string XML Output
      */
-    public function writeWorkbook(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null, $recalcRequired = false)
+    public function writeWorkbook(\PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet, $recalcRequired = false)
     {
         // Create XML writer
         if ($this->getParentWriter()->getUseDiskCaching()) {
@@ -128,7 +128,7 @@ class Workbook extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeBookViews(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null)
+    private function writeBookViews(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet)
     {
         // bookViews
         $objWriter->startElement('bookViews');
@@ -159,7 +159,7 @@ class Workbook extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeWorkbookProtection(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null)
+    private function writeWorkbookProtection(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet)
     {
         if ($spreadsheet->getSecurity()->isSecurityEnabled()) {
             $objWriter->startElement('workbookProtection');
@@ -211,7 +211,7 @@ class Workbook extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeSheets(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null)
+    private function writeSheets(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet)
     {
         // Write sheets
         $objWriter->startElement('sheets');
@@ -266,7 +266,7 @@ class Workbook extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeDefinedNames(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet = null)
+    private function writeDefinedNames(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\SpreadSheet $spreadsheet)
     {
         // Write defined names
         $objWriter->startElement('definedNames');
@@ -351,7 +351,7 @@ class Workbook extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeDefinedNameForAutofilter(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet = null, $pSheetId = 0)
+    private function writeDefinedNameForAutofilter(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet, $pSheetId = 0)
     {
         // definedName for autoFilter
         $autoFilterRange = $pSheet->getAutoFilter()->getRange();
@@ -388,7 +388,7 @@ class Workbook extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeDefinedNameForPrintTitles(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet = null, $pSheetId = 0)
+    private function writeDefinedNameForPrintTitles(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet, $pSheetId = 0)
     {
         // definedName for PrintTitles
         if ($pSheet->getPageSetup()->isColumnsToRepeatAtLeftSet() || $pSheet->getPageSetup()->isRowsToRepeatAtTopSet()) {
@@ -432,7 +432,7 @@ class Workbook extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeDefinedNameForPrintArea(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet = null, $pSheetId = 0)
+    private function writeDefinedNameForPrintArea(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet, $pSheetId = 0)
     {
         // definedName for PrintArea
         if ($pSheet->getPageSetup()->isPrintAreaSet()) {

src/PhpSpreadsheet/Writer/Xlsx/Worksheet.php

@@ -144,7 +144,7 @@ class Worksheet extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeSheetPr(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet = null)
+    private function writeSheetPr(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet)
     {
         // sheetPr
         $objWriter->startElement('sheetPr');
@@ -192,7 +192,7 @@ class Worksheet extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeDimension(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet = null)
+    private function writeDimension(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet)
     {
         // dimension
         $objWriter->startElement('dimension');
@@ -208,7 +208,7 @@ class Worksheet extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeSheetViews(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet = null)
+    private function writeSheetViews(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet)
     {
         // sheetViews
         $objWriter->startElement('sheetViews');
@@ -321,7 +321,7 @@ class Worksheet extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeSheetFormatPr(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet = null)
+    private function writeSheetFormatPr(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet)
     {
         // sheetFormatPr
         $objWriter->startElement('sheetFormatPr');
@@ -374,7 +374,7 @@ class Worksheet extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeCols(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet = null)
+    private function writeCols(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet)
     {
         // cols
         if (count($pSheet->getColumnDimensions()) > 0) {
@@ -440,7 +440,7 @@ class Worksheet extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeSheetProtection(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet = null)
+    private function writeSheetProtection(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet)
     {
         // sheetProtection
         $objWriter->startElement('sheetProtection');
@@ -476,7 +476,7 @@ class Worksheet extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeConditionalFormatting(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet = null)
+    private function writeConditionalFormatting(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet)
     {
         // Conditional id
         $id = 1;
@@ -550,7 +550,7 @@ class Worksheet extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeDataValidations(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet = null)
+    private function writeDataValidations(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet)
     {
         // Datavalidation collection
         $dataValidationCollection = $pSheet->getDataValidationCollection();
@@ -617,7 +617,7 @@ class Worksheet extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeHyperlinks(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet = null)
+    private function writeHyperlinks(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet)
     {
         // Hyperlink collection
         $hyperlinkCollection = $pSheet->getHyperlinkCollection();
@@ -659,7 +659,7 @@ class Worksheet extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeProtectedRanges(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet = null)
+    private function writeProtectedRanges(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet)
     {
         if (count($pSheet->getProtectedCells()) > 0) {
             // protectedRanges
@@ -689,7 +689,7 @@ class Worksheet extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeMergeCells(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet = null)
+    private function writeMergeCells(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet)
     {
         if (count($pSheet->getMergeCells()) > 0) {
             // mergeCells
@@ -715,7 +715,7 @@ class Worksheet extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writePrintOptions(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet = null)
+    private function writePrintOptions(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet)
     {
         // printOptions
         $objWriter->startElement('printOptions');
@@ -742,7 +742,7 @@ class Worksheet extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writePageMargins(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet = null)
+    private function writePageMargins(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet)
     {
         // pageMargins
         $objWriter->startElement('pageMargins');
@@ -763,7 +763,7 @@ class Worksheet extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeAutoFilter(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet = null)
+    private function writeAutoFilter(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet)
     {
         $autoFilterRange = $pSheet->getAutoFilter()->getRange();
         if (!empty($autoFilterRange)) {
@@ -857,7 +857,7 @@ class Worksheet extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writePageSetup(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet = null)
+    private function writePageSetup(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet)
     {
         // pageSetup
         $objWriter->startElement('pageSetup');
@@ -893,7 +893,7 @@ class Worksheet extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeHeaderFooter(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet = null)
+    private function writeHeaderFooter(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet)
     {
         // headerFooter
         $objWriter->startElement('headerFooter');
@@ -919,7 +919,7 @@ class Worksheet extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeBreaks(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet = null)
+    private function writeBreaks(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet)
     {
         // Get row and column breaks
         $aRowBreaks = [];
@@ -1201,7 +1201,7 @@ class Worksheet extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeLegacyDrawing(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet = null)
+    private function writeLegacyDrawing(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet)
     {
         // If sheet contains comments, add the relationships
         if (count($pSheet->getComments()) > 0) {
@@ -1219,7 +1219,7 @@ class Worksheet extends WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    private function writeLegacyDrawingHF(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter = null, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet = null)
+    private function writeLegacyDrawingHF(\PhpOffice\PhpSpreadsheet\Shared\XMLWriter $objWriter, \PhpOffice\PhpSpreadsheet\Worksheet $pSheet)
     {
         // If sheet contains images, add the relationships
         if (count($pSheet->getHeaderFooter()->getImages()) > 0) {

src/PhpSpreadsheet/Writer/Xlsx/WriterPart.php

@@ -40,7 +40,7 @@ abstract class WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    public function setParentWriter(\PhpOffice\PhpSpreadsheet\Writer\IWriter $pWriter = null)
+    public function setParentWriter(\PhpOffice\PhpSpreadsheet\Writer\IWriter $pWriter)
     {
         $this->parentWriter = $pWriter;
     }
@@ -67,10 +67,8 @@ abstract class WriterPart
      *
      * @throws \PhpOffice\PhpSpreadsheet\Writer\Exception
      */
-    public function __construct(\PhpOffice\PhpSpreadsheet\Writer\IWriter $pWriter = null)
+    public function __construct(\PhpOffice\PhpSpreadsheet\Writer\IWriter $pWriter)
     {
-        if (!is_null($pWriter)) {
         $this->parentWriter = $pWriter;
     }
-    }
 }

tests/PhpSpreadsheetTests/Writer/Ods/ContentTest.php

@@ -38,9 +38,7 @@ class ContentTest extends \PHPUnit_Framework_TestCase
 
     public function testWriteEmptySpreadsheet()
     {
-        $content = new Content();
+        $content = new Content(new Ods(new Spreadsheet()));
-        $content->setParentWriter(new Ods(new Spreadsheet()));
-
         $xml = $content->write();
 
         $this->assertXmlStringEqualsXmlFile($this->samplesPath . '/content-empty.xml', $xml);
@@ -91,9 +89,7 @@ class ContentTest extends \PHPUnit_Framework_TestCase
         $worksheet2->setCellValue('A1', 2);
 
         // Write
-        $content = new Content();
+        $content = new Content(new Ods($workbook));
-        $content->setParentWriter(new Ods($workbook));
-
         $xml = $content->write();
 
         $this->assertXmlStringEqualsXmlFile($this->samplesPath . '/content-with-data.xml', $xml);