note 99888 added to book.exec

All other linux commands are working except the following command <?php echo exec('wkhtmltopdf http://localhost/test.html /tmp/5.pdf'); ?> Any ideas?? ---- Server IP: 59.162.86.123 Probable Submitter: 121.240.152.4 ---- Manual Page -- http://www.php.net/manual/en/book.exec.php Edit -- https://master.php.net/note/edit/99888 Del: integrated -- https://master.php.net/note/delete/99888/integrated Del: useless -- https://master.php.net/note/delete/99888/useless Del: bad code -- https://master.php.net/note/delete/99888/bad+code Del: spam -- https://master.php.net/note/delete/99888/spam Del: non-english -- https://master.php.net/note/delete/99888/non-english Del: in docs -- https://master.php.net/note/delete/99888/in+docs Del: other reasons-- https://master.php.net/note/delete/99888 Reject -- https://master.php.net/note/reject/99888 Search -- https://master.php.net/manage/user-notes.php