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

ptg 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 Download from www.wowebook.com ptg 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. Workshop 617 20 Download from www.wowebook.com ptg 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 Download from www.wowebook.com ptg 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 Download from www.wowebook.com ptg 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 .php as 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 echo function. 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 familiar to you from the lesson on JavaScript. Just like JavaScript, PHP lets you define your own functions or use functions built in to the language. echo is a built-in function. 620 LESSON 21: Taking Advantage of the Server Download from www.wowebook.com ptg 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!” ?> Replacing php with = enables you to leave out the call to the echo function 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 Download from www.wowebook.com ptg 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 htdocs directory inside the XAMPP install directory. For example, if you want to test the hello.php page I talked about earlier, you could put it in the htdocs directory. 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 htdocs folder, 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. // $color = ‘red’; 622 LESSON 21: Taking Advantage of the Server Download from www.wowebook.com ptg 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 comment 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 $color or 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 Download from www.wowebook.com ptg 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 array function: $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 red is 0, the index of green is 1, and the index of blue is 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? $colors[8] = ‘white’; 624 LESSON 21: Taking Advantage of the Server Download from www.wowebook.com ptg 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 Download from www.wowebook.com . the HTML sent to the browser will look like this: <!DOCTYPE html& gt; < ;html& gt; <head><title>A PHP Page</title</head> <body> Hello world! </body> < /html& gt; When. 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 6 21 21 Download from www.wowebook.com ptg If. example: <!DOCTYPE html& gt; < ;html& gt; <head><title>A PHP Page</title</head> <body> <?php echo “Hello world!”; ?> </body> < /html& gt; If this page