So you might use JavaScript to make a more interesting Web page. You might use it to make the client- side of a full-fledged application, like Google Docs, that runs in the browser. You might use it to make a

Web server that talks to a Web browser. Or you might use it to make an API 31 that serves up data to a “client,” and sure, that client could be a laptop Web browser. But it’s 2015, and that client is quite probably an app on a smartphone. 5.8 What’s the Absolute Minimum I Must Know About PHP? You can get a site up and running in PHP in a few minutes, and that’s the problem. It used to be the terrible choice you made when you needed to get something done on the Web, but increasingly JavaScript has replaced it as the default terrible choice. PHP stands for Personal Home Page/Forms Interpreter. The idea was that when you loaded your Web pages, the PHP code would run before the page went out to the Internet. And PHP could, say, check whether you were logged in. If you were, it could show you your top secret account details; and if you weren’t, it could say, “Please log in.” I know a lot of people who program in PHP, and they are smart, good people. PHP powers Etsy and Facebook. It powers Wikipedia, for God’s sake. WordPress. Out of all the Web’s pages, an enormous percentage is created with PHP. Coding in PHP for a living is not a death sentence. Lots of people have gotten rich off PHP. It just means a lot of cutting and pasting, and a lot of trips to Google to figure out why things aren’t working. Poor, sad, misbegotten, incredibly effective, massively successful PHP. Reading PHP code is like reading poetry, the poetry you wrote freshman year of college. I spent so many hundreds, maybe thousands, of hours programming in PHP, back when I didn’t know what I was doing and neither did PHP. Reloading Web pages until my fingers were sore. (I can hear your sympathetic sobs.) Everything was always broken, and people were always hacking into my sites. PHP. I don’t wish it any harm. I’m glad to see how well it’s done for itself. We had some good times together. I just don’t ever want to go back there. 6 How Are Apps Made? One of the privileges of owning a Mac is that you can download a program by Apple called Xcode. This is an IDE, an Integrated Development Environment. It’s an enormous download, more than 2 gigabytes, or roughly the size of an hour of DVD-quality video. Xcode is the heart of Apple. It’s not only how the company writes software, it’s the tool for everyone who wants to write software for the Mac or iPhone. Within Xcode are whole worlds to explore. For example, one component is the iOS (Software Development Kit). You use that to make iPhone and iPad apps. That SDK is made up of dozens and dozens of APIs (Application Programming Interfaces). There’s an API for keeping track of a user’s location,