Why PHP?

There is no “right” language for every single purpose. Like wrenches in a toolbox, different programming languages lend themselves to being particularly well-suited for specific uses, although each could be massaged into handling most tasks. Choosing the right language for the job is a decision I make on a daily basis. There are compelling reasons why I usually choose PHP over another server-side scripting language such as Perl or XSSI:

It’s easy to set up. In many hosting environments PHP is set up as a module, which is a technical way of saying that if you have a file with the .php extension it will generally execute PHP code without having to change file permissions or put it in a special directory like cgi-bin. This is not universally true, but it’s the common denominator for hosts that support PHP.

Embedding bits of PHP code inside primarily XHTML pages is easy.

PHP is portable. PHP can run under Apache or IIS or thttpd on Windows or Linux or BSD or… you get the idea. This increases the value of your code and also increases your hosting mobility.

PHP is popular. Surveys show it be the most popular Apache module ever, and Apache is the most widely used Web server.

PHP is cheap. Free, actually. PHP is open source software, which means a lot of things but most importantly means that PHP is a well-supported and stable platform that is available for low- or no-cost to anyone who wants to use it. You can run PHP (and Apache and MySQL) on your home computer or on thirty enterprise servers for the same price.

Those are the objective reasons. Subjectively I think that PHP is great for getting work done elegantly and fast, is easy to learn, and has a wealth of freely available code, scripts, and documentation.
Syntax

PHP code is always contained between the wrappers . These indicate to the PHP engine that whatever is inside those starting and closing tags should be interpreted as PHP and nothing else. There are several alternate methods of indicating the same information to the PHP engine, but these are either non-standard or hinder compatibility, so for our purposes we will always use .
Comments: Say something

Comments are where you write things you don’t want executed. A single line comment may begin with two forward slashes, and nothing on the rest of that line will be interpreted by PHP. You can have multi-line comments by enclosing them between /* … */, which some of you may recognize as the comment syntax in CSS. PHP comments are great because they aren’t output to the browser at all, which can be useful when you want to make a comment for future reference, for example:

is more dangerous than

In the second example the comment will never be seen by an end-user, even if he views the HTML source. The importance of commenting your work cannot be overstated. Things that may seem obvious to you today may be opaque a year from now when they need updating. Useful comments (not silly like the one above) can save you hours and usually only take seconds to write, if you write them as you go along. Don’t tell yourself you will go back and comment things later, because chances are you won’t.
Variables: Store it

Variables are places to store information. Variable names always start with a dollar sign and then have the variable name, which can have letters, numbers, or underscores but can’t start with a number. When naming variables it is best to use succinct names that are straightforward and communicate the variable’s content.

$weather = 'Bright and sunny.';
$age = 20;
$favorite_music = 'Jazz';
?>

You will find that your variable names may need to contain more than one word. There are two ways to do this: the first is called camelCase, where the first word is lowercase and subsequent words have their first letter capitalized; the second way is by using underscores to separate the words. Both are popular, and ultimately it comes down to personal preference. I prefer the underscore method because I find it easier to read with space separating words rather just a case hump. More important than which style you choose is sticking with it and giving descriptive yet short names to your variables.
Quoting and Escaping

In XHTML, attributes must be closed within quotation marks, which may be single or double quotes. This is useful because in PHP we assign strings to variables using quotes. If you use a quote of the same kind inside the string, then it must be escaped. For example:

$link = “Example“;

As you can see we had to escape the quotes inside the string with backslashes. However taking what we know about quoting we can clean this up:

$link = “Example“;

Although single and double quotes are interchangeable in XHTML, they aren’t in PHP. Double quotes tell the PHP engine to interpret any variables it finds in the string, and single quotes tell PHP to handle the string literally. For example:

$number_cds = 42;
echo "I have $number_cds CDs.";
?>

Output: I have 42 CDs.

$number_cds = 42;
echo 'I have $number_cds CDs.';
?>

Output: I have $number_cds CDs.

Using single quotes where possible results in nominally faster execution, but we’re talking fractions of milliseconds.
Functions

PHP has hundreds of built-in functions available for you to use. Functions take a number of arguments separated by commas and do something or return something. For example the date() function can take a string of characters and output a formatted string. To output the current year we could use:

Output: 2004

How do I know that Y formats as 2004 (this year)? I looked it up quickly by typing in php.net/date which took me immediately to the reference page for the date() function. If there wasn’t a function named date, it would do a search and take me to the search results instead. This method of using the php.net Web site makes a great quick reference.
Ending Lines

We are going to finish our brief syntax overview exactly like you should end statements in PHP, with the semicolon. When you tell something to PHP, such as , the semicolon tells it the statement is done.
Execution

Now it’s time to do something useful with what we’ve learned so far. How many HTML pages have you seen that have something like this at the bottom?

Copyright © 2001-2003.

It’s pretty standard, but when it’s out of date it can look very unprofessional. Besides, after partying away New Year’s Eve, who wants to spend the next day updating the copyright dates on dozens of pages? We already know that we can echo out the current year using the date function, so lets update our example to use that and a proper en dash:

Copyright © 2001–.

The PHP code was easily embedded, and now you never have to worry about updating that year again.

If all your pages have a .html extension and aren’t set up to parse PHP code and you don’t want to have to rename every file and update every link to use the .php extension, here’s a quick line you can put in your .htaccess file (assuming you use Apache and can have a .htaccess file) to have all .html and .htm files parsed by the PHP engine.

AddType application/x-httpd.php .html .htm

What is a Web page? What, in brief, are Web pages capable of doing?
A Web page is an Internet “document” that can be accessed by Internet users with an HTML browser (such as Netscape or Microsoft). By providing the browser with a unique address, or Uniform Resource Locator (URL, variously pronounced “you-are-ell” or “earl”), you open the page with that address. Web pages commonly provide text, pictures or other graphics, and links to other pages. Newer technology also allows Web pages to provide three-dimensional images, animated images, and sound.

What does HTML stand for? What is it?
HTML, or Hypertext Markup Language, is a language that uses text and a defined set of commands (known as tags) to create most of what you see on a World Wide Web page. The tags can serve two distinct functions: They either “tell” the text how to behave (bold, italic, etc.), or make the text act as a command to insert a link, picture, or sound onto your page.

What is the best way of going about learning HTML?
Reading helps, and so does practical experience; we recommend a combination of both. You should start by finishing off the rest of this page–it gives you a manageable-sized portion of answers to questions you may have. You’ll undoubtedly have more complicated questions as you learn more.

One the best ways to learn HTML is to see how other people have done it! Using your favorite browser, find your favorite page. Then look for the “Source” or “Document Source” command under the “View” menu. This will show you a window with all of the HTML used to create that page. Look it over; more times than not, you’ll be surprised at the relatively few commands it took to put together what seemed at first like a complicated page!

What do I use to write HTML? Is there a specific piece of software?
The easiest way is to use a WYSIWYG (what you see is what you get) Web page creation program, which operates much like a word processing package and (with a bit of your help) not only writes your HTML for you, but also helps you put together your page from start to finish. These programs are especially useful for those who don’t have the time or the inclination to learn all the nuts and bolts of HTML, but you should at least have a cursory knowledge of HTML before using them.

Once people start working in HTML on a production level, they often use HTML editors, which have special features (such as automatically inserting closing tags; see below) that make HTML work fast and easy for people who know what they’re doing.

HTML files are basically simple plain ASCII text files that can be created with any text editor such as BBEdit for Macintosh, or Notepad if you are using Windows. If you don’t want to invest in either of these programs, you can use your word processor program of choice; just make sure that when you save your document, you save it as “text only with line breaks,” and make sure the filename ends in “.htm” or “.html”.

What are the required elements for an HTML document? Can you show me an example?
Every HTML document does require certain tags in order for it to work. All of the basic tags work in pairs; whatever tag you use must have a matching end tag in order for the browser to denote the beginning or end of a style or command. The only difference between the beginning and ending tag in the pair is that the / must be used with the second, or closing tag. All tags must be surrounded by < and >, but are not case-sensitive; that is, typing in HtmL will be read by the computer the same as HTML.