Explanation: Answer option A is correct.
The header() function is used to send a raw HTTP header to a client. A user should call the header() function before any actual output is sent, either by normal HTML tags, blank lines in a file, or from PHP. By sending a "Location" header instead of PHP's default, a user can cause the browser to be redirected to a new page. For example, if a Web developer wants to redirect the user to the uCertify main page on reaching his affiliate page, he will use the following code snippet in the PHP script:
header("Location: http://www.ucertify.com" );
In the above question, the user will be prompted to save a PDF file. Here, the Content-Disposition argument of the header function will supply a recommended filename and force the browser to display the save dialog box.
<?php
header("Content-type:application/pdf");
// It will be called 2.pdf
header("Content-Disposition:attachment;filename='2.pdf'");
//original file is 1.pdf
readfile("1.pdf");
?>
Answer options B, D, and C are incorrect. You will not get these outputs from the given script in the question.