PHP执行如何外部命令行

e:
cd E:\Program Files (x86)\Weeny Free Word to PDF Converter\
word2pdf.exe /source "d:\wamp\www\up1\1437027098.doc" /target "c:\My PDF"
这三条命令怎么用exec()执行，能麻烦写一下代码么?

http://www.jb51.net/article/19618.htm

<?php 
exec("/bin/ls -l"); 
exec("/bin/ls -l", $res); 
exec("/bin/ls -l", $res, $rc); 
?>