| ITEC 325 |
| 2014spring |
| ibarland |
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home—lects—hws
D2L—breeze (snow day)
What did we talk about this semester, eh?
Web Programming:
- client-side vs server-side
(where will "add to database" be? Where will "de-select checkbox if textbox is empty" be?;
#transactions made; http header info )
- php basics: functions, iteration, etc
Note: php is pass-by-value. So if I call
$_POST = tidyArray( $_POST );
(from hw04/hw04-soln/#validate.php),
how many times is the array being copied? four! (to & from function; once by me manually in loop; once by the '=' !)
- 4x copying an array of 20 items isn't going to be bad
- 4x copying large arrays when I'm trying to serve 100pages/sec? That's more serious! Pass-by-ref.
- pass-by-ref: but beware; tends to lead to hard-to-track bugs
- why not just avoid passing altogether, and use $_POST ?
Many will suggest that, but:
if you switch to GET then you'll need to write (and maintain) another copy of that function;
if is a general purpose function, you'll *want* it for all arrays.
- Handy idioms: array_map (and, array_walk), where you pass in a function [or a string -- it's name!]
- passing state between pages (since http is itself stateless)
files; cookies; sessions; database
- XML: hierarchical data (tree) marshaled to text format; human-readable; having a standard is great.
- XSLT: a langauge for XML -> XML functions.
- it is itself XML
- processed *client*-side
- uses xpath expressions (in xsl:foreach, xsl:value-of, xsl:choice etc):
xpath: expressions evaluate to a *nodeset*.
absolute vs relative paths -- relative to the node currently being handled (by template, or in loop)
filter by using [...]
- web programming: other ways.
How cool is php? Nice, low-barrier entry
But it makes me feel kinda like I'm using assembly-language:
To make a site about kittens, I need to...
have a web form, w/ fields for kitten's name, vaccination date, #claws, cuteness level, ...
do javascript validation on each of those fields
print out a kitten's info as html
have php that validates each of those fields
(maybe: php objects)
define a database table for kittens
set up SQL types/constraints for each of those fields
(maybe also: a java program that interacts with the database:
class Kitten { ... } and the constructor with all its validation code for sanity-checking.)
Oh my goodness, I don't feel so enthused about writing all this code again, in so many different languages
and in each language remembering how to call 'substring' [method or static?; end-index vs length; neg.indices allowed?] !
Do we really need a different language for each different stage?
Many before have seen this problem, and sought for a better world.
- Node.js: These are higher-level functions that do common tasks that we're coming to expect (incl. nice visual effects of I/O)
- More comprehensive approaches like: .NET, .asp, rails -- specify what info a Kitten has just once,
and let the platform will auto-generate html forms, client-side checking,
server-side validation, database def'ns, a java class, etc.
For example: c#-data-annotations.cs.
While XSLT and SQL and Java all have their own strengths,
I can also choose to use one language, and simply annotate what code is to
be performed client-side, and what to be done server-side.
Yay!
So the php/javascript in this class grounds you in the 'assembly-level' web programming:
you now know/appreciate the low-level work that needs to be done.
But don't think that just because most sites still use just php/javascript,
that it's web programming's highest level!
home—lects—hws
D2L—breeze (snow day)
| ©2014, Ian Barland, Radford University Last modified 2014.Apr.21 (Mon) |
Please mail any suggestions (incl. typos, broken links) to ibarland  radford.edu |
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