php-intro

Accompanying video:

Review: server: String → String — er, “http packet containing a URL-string, plus possibly other info like user-agent and cookies, → an http packet containing the html-string of the requested resource ¹, plus other info like the http-response-code”.
Review: show the result of requesting hello.php: the server, seeing the suffix “.php”, is configured (presumably) to run that file as a php program, and whatever that program prints is what the server sends back to the client.

SO: when our browser visits on hello.php, and we do a show-source, do we see the php program? NO! (Why not? Let's reread the above paragraph!)

I happened to take that php file, and make a copy which I (mis)named as “hello.html”. Now, the server isn't running it (since the server doesn't see any “.php” suffix), we are are being served up the file contents directly. It looks funky; do a show-source and then tell me why the client is displaying the source-code in a very odd way.

Seeing the show-source of hello.html, we can now tell what originally went on when we requested hello.php.
Task: the function blend: Given two words (like “smoke” and “smog”), we blend them to get “smog” — combine the first half of the first word, with the second half of the second word. (Linguists will want to break on syllables ² and so on; we'll be more simple-minded and just take half of each word, ignoring syllable-breaks.) Similarly, when we blend “motor” and “hotel” we get “motel”.

For any programming task (from 120 on up, including web programming), we start with test cases, which are runnable code:
echo "actual: ", blend("motor", "hotel"), "\n"; echo "expect: ", "motel", "\n"; echo "actual: ", blend("smoke", "fog"), "\n"; echo "expect: ", "smog", "\n";
In ordered to be considered a test-case, you must have:
- The expected output.
- The actual ouput (that is, actually call our function to see what it returns).
- ??? (to be revealed soon ³)
So, let's make some further test cases. What should blend("Christiansburg", "Virginia") return?
What should blend("Radford", "Univ.") return?

We'll continue next time: What other inputs should we test?

¹Or if the requested resource was (say) in image-file, the http packet's payload would be the bits of the image-file. The payload is actually reponsible for includeing a “mime-type” statement to help the receiver understand how the payload's bits should be interpreted, but it's forgivable to think of the payload as just being the bits all the other meta-information as part of some-header-or-another, w/o worrying to distinguish http header info from other headers. ↩

² For example, see www.montgomerycollege.edu/~steuben/blendwords.htm. ↩

³Okay, okay, here's the third component right now: A way to automatically compare the actual and expected outputs, so that we don't rely on having to manually scour output with a human eye. ↩

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