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You can ask the iTunes team for a refund. There's a guide for this at http://gizmodo.com/5886683/how-to-get-a-refund-from-the-app-store
Textastic offers syntax highlighting for many languages including PHP, but it doesn't include compilers or interpreters due to restrictions of iOS.
If you try to preview the php file locally, only the html part will be interpreted by the web view. The PHP part will be ignored.
In order to preview PHP in Textastic, you can upload the file to a test server, open the preview screen,
and enter the remote url of your test server.
As Dave pointed out above, you also need to add <html debug="true"> to your html document when you do that.
Instead of using the feature in Textastic, you can reference Firebug Lite directly in your html file as described at http://getfirebug.com/firebuglite#Stable:
<script type="text/javascript" src="https://getfirebug.com/firebug-lite.js"></script>
This way it will be loaded with the web page.
Textastic for Mac is now available on the Mac App Store: https://itunes.apple.com/us/app/textastic/id572491815?mt=12
Customer support service by UserEcho
I tried to follow the steps on my machine and it worked without a problem. Which Mac OS X version do you use? I tried it on 10.8.3.