Use ?-> operator instead

src/PhpSpreadsheet/Calculation/LookupRef/Indirect.php

@@ -106,7 +106,7 @@ class Indirect
      */
     private static function extractRequiredCells(?Worksheet $worksheet, string $cellAddress): array
     {
-        return Calculation::getInstance($worksheet !== null ? $worksheet->getParent() : null)
+        return Calculation::getInstance($worksheet?->getParent())
             ->extractCellRange($cellAddress, $worksheet, false, createCell: true);
     }
 

src/PhpSpreadsheet/Calculation/LookupRef/Offset.php

@@ -102,7 +102,7 @@ class Offset
     /** @return mixed[] */
     private static function extractRequiredCells(?Worksheet $worksheet, string $cellAddress): array
     {
-        return Calculation::getInstance($worksheet !== null ? $worksheet->getParent() : null)
+        return Calculation::getInstance($worksheet?->getParent())
             ->extractCellRange($cellAddress, $worksheet, false);
     }
 

src/PhpSpreadsheet/Writer/Xls/Workbook.php

@@ -551,7 +551,7 @@ class Workbook extends BIFFwriter
             if (empty($worksheet)) {
                 if (($offset === 0) || ($definedRange[$offset - 1] !== ':')) {
                     // We should have a worksheet
-                    $worksheet = $definedName->getWorksheet() ? $definedName->getWorksheet()->getTitle() : null;
+                    $worksheet = $definedName->getWorksheet()?->getTitle();
                 }
             } else {
                 $worksheet = str_replace("''", "'", trim($worksheet, "'"));