fix: fix minor issues detected by phpstan

GitOrigin-RevId: e6e0802ef8b942d2307249e2b6167e2b8f9047d1
diff --git a/src/doexport.php b/src/doexport.php
index 6326fc9..bb57acb 100644
--- a/src/doexport.php
+++ b/src/doexport.php
@@ -77,7 +77,7 @@
 
   $actualTime = time();
 
-  class PDF extends EXFPDF {
+  class PDF extends exFPDF {
     function Footer() {
       global $actualTime;