Let's have a nice look at the pros and cons of Flash:
Pros
Respect from people who aren't good at Flash
Good pay per job
Cons
Jobs can take forever to complete, lowering the amount of money you can make
To get the most out of it, you need to learn a scripting language anyways
Some people can't view Flash documents in a browser
Flash just pisses me off :P
Now let's take a look at the pros and cons of PHP:
Pros
Extremely versatile
Easy to get into, challenging to master
High demand for PHP coders
Can be done in any word processing application
You can work on your scripts from any computer, unlike with Flash
Works on all browsers that support HTML, since it converts the info to HTML before displaying it
Cons
Requires hosting with PHP support
Finger cramps :P
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Needless to say, PHP would be the more senseable route to choose if you're looking to make money
