Professional Information Technology-Programming Book part 61 docx

Your First Script
Before you go any further, you need to make sure you can create and run PHP
scripts as you go through the examples in this book. This could be on your own
machine, and you can find instructions for installing PHP in Appendix A,
"Installing PHP." Also, many web hosting companies include PHP in their
packages, and you may already have access to a suitable piece of web space.
Go ahead and create a new file called time.php that contains Listing 1.1, in a
location that can be accessed by a PHP-enabled web server. This is a slight
variation on the date example shown previously.
Listing 1.1. Displaying the System Date and Time
The time is
<?php echo date('H:i:s');?>
and the date is
<?php echo date('j F Y');?>

When you enter the URL to this file in your web browser, you should see the
current date and time, according to the system clock on your web server, displayed.

Running PHP Locally
If you are running PHP from your local PC,
PHP code in a script will be executed only if it is accessed through
a web server that has the PHP module enabled. If you open a local
script directly in the web browserfor instance, by double-clicking
or dragging and dropping the file into the browserit will be treated
as HTML only.

Web Document Location If you were using a default Apache
installation in Windows, you would create time.php in the
folder C:\Program Files\Apache
Group\Apache\htdocs, and the correct URL would be
http://localhost/time.php.

If you entered Listing 1.1
exactly as shown, you might notice that the actual output
produced could be formatted a little betterthere is no space between the time and
the word and. Any line in a script that only contains code inside PHP tags will not
take up a line of output in the generated HTML.
If you use the View Source option in your web browser, you can see the exact
output produced by your script, which should look similar to the following:
The time is
15:33:09and the date is
13 October 2004

If you insert a space character after ?>, that line now contains non-PHP elements,
and the output is spaced correctly.
The echo Command
While PHP is great for embedding small, dynamic elements inside a web page, in
fact the whole page could consist of a set of PHP instructions to generate the
output if the entire script were enclosed in PHP tags.
The echo command is used to send output to the browser. Listing 1.1 uses echo
to display the result of the date command, which returns a string that contains a
formatted version of the current date. Listing 1.2 does the same thing but uses a
series of echo commands in a single block of PHP code to display the date and
time.
Listing 1.2. Using echo to Send Output to the Browser
<?php
echo "The time is ";
echo date('H:i:s');
echo " and the date is ";
echo date('j F Y');
?>

The non-dynamic text elements you want to output are contained in quotation
marks. Either double quotes (as used in Listing 1.2) or single quotes (the same
character used for an apostrophe) can be used to enclose text strings, although you
will see an important difference between the two styles in Lesson 2, "Variables."
The following statements are equally valid:
echo "The time is ";
echo 'The time is ';

Notice that space characters are used in these statements inside the quotation marks
to ensure that the output from date is spaced away from the surrounding text. In
fact the output from Listing 1.2 is slightly different from that for Listing 1.1, but in
a web browser you will need to use View Source to see the difference. The raw
output from Listing 1.2 is as follows:
The time is 15:59:50 and the date is 13 October 2004

There are no line breaks in the page source produced this time. In a web browser,
the output looks just the same as for Listing 1.1 because in HTML all whitespace,
including carriage returns and multiple space or tab characters, is displayed as a
single space in a rendered web page.
A newline character inside a PHP code blo
ck does not form part of the output. Line
breaks can be used to format the code in a readable way, but several short
commands could appear on the same line of code, or a long command could span
several linesthat's why you use the semicolon to indicate the end of a command.
Listing 1.3 is identical to Listing 1.2 except that the formatting makes this script
almost unreadable.
Listing 1.3. A Badly Formatted Script That Displays the Date and Time
<?php echo "The time is "; echo date('H:i:s'); echo
" and the date is "

; echo date(
'j F Y'
);
?>

Using Newlines If you wanted to send an explicit newline
character to the web browser, you could use the character
sequence \n. There are several character sequences like this that
have special meanings, and you will see more of them in Lesson
6, "Working with Strings."

Comments
Another way to make sure your code remains readable is by adding
comments to it.
A comment is a piece of free text that can appear anywhere in a script and is
completely ignored by PHP. The different comment styles supported by PHP are
shown in Table 1.1.
Table 1.1. Comment Styles in PHP
Comment Description
// or #
Single-line comment. Everything to the end of the current line is
ignored.
/*
*/
Single- or multiple-line comment. Everything between /* and */
is ignored.

Listing 1.4 produces the same formatted date and time as Listings 1.1, 1.2, and 1.3
,
but it contains an abundance of comments. Because the comments are just ignored

by PHP, the output produced consists of only the date and time.
Listing 1.4. Using Comments in a Script
<?php
/* time.php
This script prints the current date
and time in the web browser
*/

echo "The time is ";
echo date('H:i:s'); // Hours, minutes, seconds

echo " and the date is ";
echo date('j F Y'); // Day name, month name, year
?>

Listing 1.4 includes a header comment block that contains the filename and a brief
description, as well as inline comments that show what each date command will
produce.



Summary
In this lesson you have learned how PHP works in a web environment, and you
have seen what a simple PHP script looks like. In the next lesson you will learn
how to use variables.




Lesson 2. Variables

In this lesson you will learn how to assign values to variables in PHP and use them
in some simple expressions.