diff --git a/src/PhpSpreadsheet/Reader/Xlsx.php b/src/PhpSpreadsheet/Reader/Xlsx.php
index 4222b954..eafa36b5 100644
--- a/src/PhpSpreadsheet/Reader/Xlsx.php
+++ b/src/PhpSpreadsheet/Reader/Xlsx.php
@@ -532,7 +532,7 @@ class Xlsx extends BaseReader
                             $excel->addCellXf($objStyle);
                         }
 
-                        foreach (isset($xmlStyles->cellStyleXfs->xf) ? $xmlStyles->cellStyleXfs->xf : [] as $xf) {
+                        foreach ($xmlStyles->cellStyleXfs->xf ?? [] as $xf) {
                             $numFmt = NumberFormat::FORMAT_GENERAL;
                             if ($numFmts && $xf['numFmtId']) {
                                 $tmpNumFmt = self::getArrayItem($numFmts->xpath("sml:numFmt[@numFmtId=$xf[numFmtId]]"));
@@ -1148,7 +1148,7 @@ class Xlsx extends BaseReader
                                                         $shadow->setDistance(Drawing::EMUToPixels(self::getArrayItem($outerShdw->attributes(), 'dist')));
                                                         $shadow->setDirection(Drawing::angleToDegrees(self::getArrayItem($outerShdw->attributes(), 'dir')));
                                                         $shadow->setAlignment((string) self::getArrayItem($outerShdw->attributes(), 'algn'));
-                                                        $clr = isset($outerShdw->srgbClr) ? $outerShdw->srgbClr : $outerShdw->prstClr;
+                                                        $clr = $outerShdw->srgbClr ?? $outerShdw->prstClr;
                                                         $shadow->getColor()->setRGB(self::getArrayItem($clr->attributes(), 'val'));
                                                         $shadow->setAlpha(self::getArrayItem($clr->alpha->attributes(), 'val') / 1000);
                                                     }
@@ -1201,7 +1201,7 @@ class Xlsx extends BaseReader
                                                         $shadow->setDistance(Drawing::EMUToPixels(self::getArrayItem($outerShdw->attributes(), 'dist')));
                                                         $shadow->setDirection(Drawing::angleToDegrees(self::getArrayItem($outerShdw->attributes(), 'dir')));
                                                         $shadow->setAlignment((string) self::getArrayItem($outerShdw->attributes(), 'algn'));
-                                                        $clr = isset($outerShdw->srgbClr) ? $outerShdw->srgbClr : $outerShdw->prstClr;
+                                                        $clr = $outerShdw->srgbClr ?? $outerShdw->prstClr;
                                                         $shadow->getColor()->setRGB(self::getArrayItem($clr->attributes(), 'val'));
                                                         $shadow->setAlpha(self::getArrayItem($clr->alpha->attributes(), 'val') / 1000);
                                                     }
diff --git a/src/PhpSpreadsheet/Shared/JAMA/Matrix.php b/src/PhpSpreadsheet/Shared/JAMA/Matrix.php
index a5cb6de0..5182993c 100644
--- a/src/PhpSpreadsheet/Shared/JAMA/Matrix.php
+++ b/src/PhpSpreadsheet/Shared/JAMA/Matrix.php
@@ -1164,7 +1164,7 @@ class Matrix
      *
      * @return Matrix ... Solution if A is square, least squares solution otherwise
      */
-    public function solve($B)
+    public function solve(self $B)
     {
         if ($this->m == $this->n) {
             $LU = new LUDecomposition($this);
diff --git a/src/PhpSpreadsheet/Shared/OLE/PPS.php b/src/PhpSpreadsheet/Shared/OLE/PPS.php
index cf764d0b..a90f193b 100644
--- a/src/PhpSpreadsheet/Shared/OLE/PPS.php
+++ b/src/PhpSpreadsheet/Shared/OLE/PPS.php
@@ -189,7 +189,7 @@ class PPS
             . "\x00\x00\x00\x00"                  // 100
             . OLE::localDateToOLE($this->Time1st)          // 108
             . OLE::localDateToOLE($this->Time2nd)          // 116
-            . pack('V', isset($this->startBlock) ? $this->startBlock : 0)  // 120
+            . pack('V', $this->startBlock ?? 0)  // 120
             . pack('V', $this->Size)               // 124
             . pack('V', 0); // 128
 
diff --git a/src/PhpSpreadsheet/Writer/Xls/Workbook.php b/src/PhpSpreadsheet/Writer/Xls/Workbook.php
index f752bce6..2b4895f0 100644
--- a/src/PhpSpreadsheet/Writer/Xls/Workbook.php
+++ b/src/PhpSpreadsheet/Writer/Xls/Workbook.php
@@ -757,7 +757,7 @@ class Workbook extends BIFFwriter
      *
      * @param string $name
      * @param string $sheetIndex 1-based sheet index the defined name applies to. 0 = global
-     * @param integer[][] $rangeBounds range boundaries
+     * @param int[][] $rangeBounds range boundaries
      * @param bool $isHidden
      *
      * @return string Complete binary record data