Firstly, in order to view your PHP, you will need a PHP interpreter (php.exe) and a server on which to run a browser to display your PHP.
Probably the most popular Widows (you didn't specify, so I am guessing) WAMP setups is XAMPP: You can download the portable version from here, or use another of your choice.
After that, use the portable version of your favourite PHP IDE, or search for something else.
The most popular/powerful is PHPstorm and there is a portable version of the Community Edition here.
Before using that, I used CodeLobster for PHP for years. The free protable edition can be downloaded from here.
I also used NetBeans for years, for many languages, including PPH. The free portable edition is here.