Tự học HTML và CSS trong 1 giờ - part 65 ppsx

You learned what a web server does and how to get one, how to organize your files and install them on the server, and how to find your URL and use it to test your pages.. LESSON 21 Takin

Other numbers on the page provide insight into how users are interacting with your site

Bounce Rate shows the percentage of users who leave after visiting your landing page

instead of sticking around to visit more pages on your site The average pages per visit

and average time on site provide a further idea of the degree to which users are drilling

down on your site In some cases, low numbers here may be fine If your page is a set of

links to other sites, a high bounce rate and low time on the site may indicate that users

are finding what they’re looking for and following the links Your interpretation of the

statistics should be based on your goals

Each of the reports on the Dashboard links to a report with more detailed information

For example, if you click the report link for Traffic Sources, you’ll see a more detailed

breakdown of where your traffic originated, including which search terms people used to

find your site

One report shows which browsers and operating systems your visitors are using, so that

you can figure out which features your audiences will be able to take advantage of Other

reports show how many of your users visited for the first time and how many are repeat

visitors There are reports that show which sites link to yours Keeping a close eye on

your Analytics reports will enable you to figure out which parts of your site are working

and which aren’t, whether you use Google Analytics or some other analytics package

Summary

In this lesson, you published your site on the Web through the use of a web server, either

one installed by you or that of a network provider You learned what a web server does

and how to get one, how to organize your files and install them on the server, and how to

find your URL and use it to test your pages You also learned the many ways that you

can advertise and promote your site, and how to use log files and Google Analytics to

keep track of the number of visitors At last, you’re on the Web and people are coming

to visit!

Workshop

As always, we wrap up the lesson with a few questions, quizzes, and exercises Here are

some pointers and refreshers on how to promote your website

616 LESSON 20: Putting Your Site Online

Q&A

Q I’ve published my pages at an ISP I really like The URL is something like

http://www.thebestisp.com/users/mypages/ Instead of this URL, I’d like to

have my own hostname, something like http://www.mypages.com/ How can I

do this?

A You have two choices The easiest way is to ask your ISP whether you’re allowed

to have your own domain name Many ISPs have a method for setting up your

domain so that you can still use their services and work with them—it’s only your

URL that changes Note that having your own hostname might cost more money,

but it’s the way to go if you really must have that URL Many web hosting services

have plans starting as low as $5 a month for this type of service, and it currently

costs as little as $16 to register your domain for two years

The other option is to set up your own server with your own domain name This

option could be significantly more expensive than working with an ISP, and it

requires at least some background in basic network administration

Q There are so many search engines! Do I have to add my URL to all of them?

A No, mainly because eventually they will find your site whether you add it to them

or not Adding your URL to a search engine may get it into the results more

quickly, so if you already know about a search engine and can submit your site, do

so Otherwise, don’t worry about it

Quiz

1 What’s the basic function of a web server?

2 What are default index files, and what’s the advantage of using them in all

directo-ries?

3 What are some things that you should check immediately after you upload your

web pages?

4 Name some of the ways that you can promote your website

5 What’s a hit?

Quiz Answers

1 A web server is a program that sits on a machine connected to the Internet (or an

intranet) It determines which resource is associated with a URL and delivers that

resource to the user

20

2 The default index file is loaded when a URL ends with a directory name rather

than a filename Typical examples of default index files are index.html,

index.htm, and default.htm If you use default filenames, you can use a URL

such as http://www.mysite.com/ rather than http://www.mysite.com/index.html to

get to the home page in the directory

3 Make sure that your browser can reach your web pages on the server, that you can

access the files on your website, and that your links and images work as expected

After you’ve determined that everything appears the way you think it should, have

your friends and family test your pages in other browsers

4 Some ways you can promote your site include major web directories and search

engines, listings on business cards and other promotional materials, and web rings

5 A hit is a request for any file from your website

Exercises

1 Start shopping around and consider where you want to host your website Find a

couple of web hosting firms that look like good options and do some research

online to see what their existing customers have to say about them

2 Upload and test a practice page to learn the process, even if it’s just a blank page

that you’ll add content to later You might work out a few kinks this way before

you actually upload all your hard work on the Web

3 Visit some of the search engines listed in this lesson to obtain a list of the sites

where you want to promote your web page Review each of the choices to see

whether there are special requirements for listing your page

4 Sign up for a Google Analytics account and install it on your site Explore the

reports to see what kind of information it provides about your site

618 LESSON 20: Putting Your Site Online

LESSON 21

Taking Advantage of

the Server

At this point, you’ve learned how to publish websites using Hypertext

Markup Language (HTML) This lesson takes things a step further and

explains how to build dynamic websites using scripts on the server Most

websites utilize some kind of server-side processing Search engines take

the user’s request and search an index of web pages on the server

Online stores use server-side processing to look up items in the

inven-tory, keep track of the user’s shopping cart, and handle the checkout

process Newspaper websites keep articles in a database and use

server-side processing to generate the article pages This lesson

intro-duces server-side programming using the PHP language PHP is the most

common scripting platform provided by web hosts, can be easily installed

on your own computer, and is completely free It’s also easy to get

started with Even if you wind up developing your applications using some

other scripting language, you can apply the principles you’ll learn in this

lesson to those languages

In this lesson, you’ll learn the following:

n How PHP works

n How to set up a PHP development environment

n The basics of the PHP language

n How to process form input

n Using PHP includes

How PHP Works

PHP enables programmers to include PHP code in their HTML documents, which is

processed on the server before the HTML is sent to the browser Normally, when a user

submits a request to the server for a web page, the server reads the HTML file and sends

its contents back in response If the request is for a PHP file and the server supports PHP,

the server looks for PHP code in the document, executes it, and includes the output of

that code in the page in place of the PHP code Here’s a simple example:

<!DOCTYPE html>

<html>

<head><title>A PHP Page</title</head>

<body>

<?php echo “Hello world!”; ?>

</body>

</html>

If this page is requested from a web server that supports PHP, the HTML sent to the

browser will look like this:

<!DOCTYPE html>

<html>

<head><title>A PHP Page</title</head>

<body>

Hello world!

</body>

</html>

When the user requests the page, the web server determines that it is a PHP page rather

than a regular HTML page If a web server supports PHP, it usually treats any files with

the extension .phpas PHP pages Assuming this page is called something like

hello.php, when the web server receives the request, it scans the page looking for PHP

code and then runs any code it finds PHP code is distinguished from the rest of a page

by PHP tags, which look like this:

<?php your code here ?>

Whenever the server finds those tags, it treats whatever is within them as PHP code

That’s not so different from the way things work with JavaScript, where anything inside

<script>tags is treated as JavaScript code

In the example, the PHP code contains a call to the echofunction This function prints

out the value of whatever is passed to it In this case, I passed the text “Hello world!” to

the function, so that text is included in the page The concept of functions should also be

620 LESSON 21: Taking Advantage of the Server

Statements in PHP, as in JavaScript, are terminated with a semicolon (You can see the

semicolon at the end of the statement in the example.) There’s no reason why you can’t

include multiple statements within one PHP tag, like this:

<?php

echo “Hello “;

echo “world!”;

?>

PHP also provides a shortcut if all you want to do is print the value of something to a

page Instead of using the full PHP tag, you can use the expression tag, which just

echoes a value to the page Instead of using

<?php echo “Hello world!”; ?>

You can use this:

<?= “Hello world!” ?>

Replacingphpwith=enables you to leave out the call to the echofunction and the

semi-colon This style of tag is referred to as a short tag Not all PHP installations have short

tags enabled

Getting PHP to Run on Your Computer

Before you can start writing your own PHP scripts, you need to set up a PHP

environ-ment The easiest approach is probably to sign up for a web hosting account that

pro-vides PHP support Even if you do so, though, there are some advantages to getting PHP

to work on your own computer You can edit files with your favorite editor and then test

them right on your own computer rather than uploading them to see how they work

You’ll also be able to work on them even if you’re not online Finally, you can keep from

putting files on a server that your users see without your having tested them first

To process PHP pages, you need the PHP interpreter and a web server that works with

the PHP interpreter The good news is that PHP and the most popular web server,

Apache, are both free, open source software The bad news is that getting PHP up and

running can be a bit of a technical challenge

Fortunately, if you’re a Windows or Mac user, someone else has done this hard work for

you A tool called XAMPP, available for both Windows and OS X, bundles up versions

of Apache, PHP, and MySQL (a database useful for storing data associated with web

applications) that are already set up to work together (The last P is for Perl, another

script-ing language.) You can download it from http://www.apachefriends.org/en/xampp.html

Getting PHP to Run on Your Computer 621

21

If you’re a Mac user, you also have the option of using MAMP, another free package that

combines Apache, PHP, and MySQL It can be downloaded from http://www.mamp.info

Mac users also have the option of using the version of Apache and PHP that are included

with OS X

After you’ve installed XAMPP (or MAMP), you just have to start the application to get a

web server up and running that you can use to develop your pages To test your PHP

pages, you can put them in the htdocsdirectory inside the XAMPP install directory For

example, if you want to test the hello.phppage I talked about earlier, you could put it in

thehtdocsdirectory To view it, just go to http://localhost/hello.php

If that doesn’t work, make sure that XAMPP has started the Apache server If you’re

using MAMP, the steps are basically the same Just put your pages in the htdocsfolder,

as with XAMPP

The PHP Language

When you think about the English language, you think about it in terms of parts of

speech Nouns name things, verbs explain what things do, adjectives describe things, and

so on Programming languages are similar A programming language is made up of

vari-ous “parts of speech,” too In this section, I explain the parts of speech that make up the

PHP language—comments, variables, conditional statements, and functions

It might be helpful to think back to the lesson on JavaScript as you read this lesson PHP

and JavaScript share a common ancestry, and many of the basic language features are

similar between the two If things such as the comment format, curly braces, and control

statements look similar from one to the other, it’s because they are

Comments

Like HTML and JavaScript, PHP supports comments PHP provides two comment

styles: one for single-line comments, and another for multiple comments (If you’re

familiar with comments in the C or Java programming language, you’ll notice that PHP’s

are the same.) First, single-line comments To start a single-line comment, use //or#

Everything that follows either on a line is treated as a comment Here are some

exam-ples:

// My function starts here.

$color = ‘red’; // Set the color for text on the page

# $color = ‘blue’;

$color = $old_color; # Sets the color to the old color.

622 LESSON 21: Taking Advantage of the Server

The text that precedes //is processed by PHP, so the second line assigns the $color

variable On the third line, I’ve turned off the assignment by commenting it out PHP

also supports multiple-line comments, which begin with /*and end with */ If you want

to comment out several lines of code, you can do so like this:

/*

$color = ‘red’;

$count = 55; // Set the number of items on a page.

// $count = $count + 1;

*/

PHP ignores all the lines inside the comments Note that you can put the //style

com-ment inside the multiline comcom-ment with no ill effects You cannot, however, nest

multi-line comments This is illegal:

/*

$color = ‘red’;

$count = 55; // Set the number of items on a page.

/* $count = $count + 1; */

*/

The PHP Language 623

21

The generally accepted style for PHP code is to use // for single-line comments rather than #

Variables

Variables just provide a way for the programmers to assign a name to a piece of data In

PHP, these names are preceded by a dollar sign ($) Therefore, you might store a color in

a variable called $coloror a date in a variable named $last_published_at Here’s how

you assign values to those variables:

$color = “red”;

$last_published_at = time();

The first line assigns the value “red”to$color; the second returns the value returned by

the built-in PHP function time()to$last_published_at That function returns a

time-stamp represented as the number of seconds since the “UNIX epoch.”

One thing you should notice here is that you don’t have to indicate what kind of

item you’ll be storing in a variable when you declare it You can put a string in it,

as I did when I assigned “red”to$color You can put a number in it, as I did with

$last_published_at I know that the number is a timestamp, but as far as PHP is

NOTE

concerned, it’s just a number What if I want a date that’s formatted to be displayed

rather than stored in seconds so that it can be used in calculations? I can use the PHP

date()function Here’s an example:

$last_published_at = date(“F j, Y, g:i a”);

This code formats the current date so that it looks something like “June 10, 2010, 8:47

pm.” As you can see, I can change what kind of information is stored in a variable

with-out doing anything special It just works The only catch is that you have to keep track of

what sort of thing you’ve stored in a variable when you use it For more information

about how PHP deals with variable types, see

http://www.php.net/manual/en/language.types.type-juggling.php

Despite the fact that variables don’t have to be declared as being associated with a

partic-ular type, PHP does support various data types, including string, integer, and float (for

numbers with decimal points) Not all variable types work in all contexts One data type

that requires additional explanation is the array data type

Arrays

The variables you’ve seen so far in this lesson have all been used to store single values

Arrays are data structures that can store multiple values You can think of them as lists of

values, and those values can be strings, numbers, or even other arrays To declare an

array, use the built-in arrayfunction:

$colors = array(‘red’, ‘green’, ‘blue’);

This declaration creates an array with three elements in it Each element in an array is

numbered, and that number is referred to as the index For historical reasons, array

indexes start at 0, so for the preceding array, the index of redis 0, the index of greenis

1, and the index of blueis 2 You can reference an element of an array using its index,

like this:

$color = $colors[1];

By the same token, you can assign values to specific elements of an array, too, like this:

$colors[2] = ‘purple’;

You can also use this method to grow an array, as follows:

$colors[3] = ‘orange’;

What happens if you skip a few elements when you assign an item to an array, as in the

following line?

624 LESSON 21: Taking Advantage of the Server

In this case, not only will element 8 be created, but elements 4 through 7 will be created,

too If you want to add an element onto the end of an array, you just leave out the index

when you make the assignment, like this:

$colors[] = ‘yellow’;

In addition to arrays with numeric indexes, PHP supports associative arrays, which have

indexes supplied by the programmer These are sometimes referred to as dictionaries or

as hashes Here’s an example that shows how they are declared:

$state_capitals = array(

‘Texas’ => ‘Austin’,

‘Louisiana’ => ‘Baton Rouge’,

‘North Carolina’ => ‘Raleigh’,

‘South Dakota’ => ‘Pierre’

);

When you reference an associative array, you do so using the keys you supplied, as

fol-lows:

$capital_of_texas = $state_capitals[‘Texas’];

To add a new element to an associative array, you just supply the new key and value, like

this:

$state_capitals[‘Pennsylvania’] = ‘Harrisburg’;

If you need to remove an element from an array, just use the built-in unset()function,

like this:

unset($colors[1]);

The element with the index specified will be removed, and the array will decrease in size

by one element, too The indexes of the elements with larger indexes than the one that

was removed will be reduced by one You can also use unset()to remove elements from

associative arrays, like this:

unset($state_capitals[‘Texas’]);

Array indexes can be specified using variables You just put the variable reference inside

the square brackets, like this:

$i = 1;

$var = $my_array[$i];

This also works with associative arrays:

$str = ‘dog’;

$my_pet = $pets[$str];

The PHP Language 625

21