If I create a test.php file with the following code, I put that test.php on the website. the code will show the pdf on the screen. It works ok.
<?php
header("Content-Type: application/pdf");
@readfile($pdfFile);
?>

But if I put  these few lines of code in my php, it does not show the pdf file on the screen.
<?php
$pdffile = myCreatePDF_function($myHTML);
//I know my pdf file is created, because if I stop here, I can see my pdf file and I can use my test.php to show my pdf file on screen.
//But if I put the code in here. It does not work.
header("Content-Type: application/pdf");
@readfile($pdfFile);
exit();
?>

Can anyone tell me why?

Any comments are highly appreciated.

Cindy