refactor method call

export.php

@@ -7,13 +7,25 @@ if (empty($_POST["test_cases"])) {
     die();
 }
 
-// split input by line and place into template at cell B2
+// split input by line
 $cases = explode("\n", $_POST["test_cases"]);
-$excel = PHPExcel_IOFactory::load("template.xlsx");
-$excel->getActiveSheet()->fromArray(array_chunk($cases, 1), NULL, 'B2');
 
 // set the right download headers
 header('Content-Type: application/vnd.ms-excel');
 header('Content-Disposition: attachment;filename="testcase-template.xls"');
 header('Cache-Control: max-age=0');
-PHPExcel_IOFactory::createWriter($excel, 'Excel5')->save('php://output');
+
+PHPExcel_IOFactory::createWriter(
+    PHPExcel_IOFactory::load("template.xlsx")
+        ->getActiveSheet()
+        ->fromArray(
+            // place vertically
+            array_chunk($cases, 1)
+            // skip NULLs
+            , NULL
+            // starting at B2
+            , 'B2'
+            )
+    , 'Excel5'
+// save to request page
+)->save('php://output');