Is it possible to view the PHP code of a live website ?
No, as it is interpreted on the server-side and the results are sent to the user. If you want to view the source code of a site you control in-browser, consider the FirePHP extension for Firebug, or just access your site files with your preferred method.
Do you have access to the files on the live server? If so yes, otherwise no, it is only possible to see the result of the script execution.
Not if PHP is configured properly.
PHP is served already interpreted to the visitor.
Seeing the PHP code on a live website would be considered hacking which is probably outside the ethical scope of stackoverflow.
No, unless the server admin screwed up. And sometimes happens... that's why facebook made a patch for this
Usually, no, as others have said, unless of course this is something you want to be the case. Then you can set it up so that using .phps (or any other extension really, but this is the norm) will display the source code of the page (with syntax coloring I believe). Something like:
AddHandler application/x-httpd-php-source .phps
in your apache configuration should do the trick.
Note, you will need to save your .php files with a .phps for their source to be displayed.
Yes: ssh to it, go to the directory hold the source file, say 'index.php', and "cat" it:
ssh myserver.com
cd ~/www
cat index.php | less
There you go!
NOTE: this is a joke.
There are a few sites that allow you to view their PHP source. Try googling for inurl:viewsource.php (my site should turn up in there somewhere :)).
Also you can view php.net's source: http://www.php.net/source.php?url=/index.php
Well, this has been fairly well answered, but on the strength in numbers fallacy, let me add:
Generally, no.
Everyone is wrong! Yes, it is possible! But if you do see the code in your web browser then this would be a serious security breach or some major trouble in the web server. I've seen it happen once, where some dumb administrator had removed the PHP extension for IIS thus the browser provided all sources as text files instead of executing them.
Then again, there is an alternative method, which is through FTP. Most websites give access to their file system through FTP, so administrators don't need physical access to the system. You will need to know username and password, plus the FTP address to get access, but once you have this information, you have access to the whole site. Useful for administrators, yet also a very good reason to be very careful with passwords.