PHP Developer''''s Dictionary- P7 pdf
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PHP Developer’s Dictionary
IT-SC book
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Chapter 2. Generating HTML
As Web sites become more and more user friendly, Web publishers want the content
to be more attractive and tailored to the tastes of each user. Visit any of the top-tier
Web sites today and each of them will offer some type of customization based on
your preferences. This customization might be in the form of personalized weather,
stock quotes, or news. Each of these preferences is read from a database based on
your login ID or a cookie value that is passed in from your browser.
This section describes some of the methods for generating dynamic content by using
PHP. We discuss the use of variables in generating content and how to use the
environment, dates, and times to affect what the user sees. We also discuss sending
email from within PHP and using PHP to authenticate to a Web site.
Generating Dynamic Content
This section defines dynamic content and then discusses practical ways to generate
content. The dynamic contents discussed in this section are limited to using request
variables and the environment to generate content. Other methods, namely using
databases to generate content, will be discussed in the next chapter.
Defining Dynamic Content
Let's first define dynamic content.
Dynamic content
is where the user's Web
experience is determined by outside influences. This means that content seen on a
site in the morning, without intervention from the Webmaster, will change in the
afternoon, and possibly again at night.
Using Request Variables to Generate Content
PHP can use a number of variables to generate dynamic content. Table 2.1 describes
the environment variables that are available to the PHP script.
Table 2.1. PHP Variables
Variable
Description
argv
argv is defined as an array of arguments passed to the script on
the command line. This functionality gives a C-like look and feel
to command-line parameters. When the PHP script is called using
the
GET
method,
argv
will contain any query string information.
argc
argc
is defined as the number of command-line parameters
passed to the script. This adds a C-like look and feel to running
the PHP scripts from the command line.
PHP_SELF
PHP_SELF
is defined as the current executing PHP script. This
allows the script to pass variables to itself based on input.
HTTP_COOKIE_VARS
HTTP_COOKIE_VARS
is defined as an associative array of variables
passed to the PHP script containing the client's cookies.
HTTP_GET_VARS
HTTP_GET_VARS
is defined as an associative array of variables
passed to the PHP script by a client using the HTTP
GET
method.
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HTTP_POST_VARS
HTTP_POST_VARS
is defined as an associative array of variables
passed to the PHP script by a client using the HTTP POST method.
These variables are accessed through the use of PHP variables. To illustrate how
different types of information can be passed from one Web page to a PHP script,
consider the following example:
<HTML>
<HEAD>
<TITLE>Posting Variables</TITLE>
<BODY>
<CENTER>Enter the following information:
<P>
<TABLE width="200"><TR><TD align="left">
<FORM ACTION="phpvariables.php?ITEM=10" METHOD="POST">
Your name:<BR>
<INPUT TYPE="text" NAME="name" SIZE="20" MAXLENGTH="30">
<P>
Your email address:<BR>
<INPUT TYPE="text" NAME="email" SIZE="20" MAXLENGTH="30">
<P>
I prefer:
<SELECT NAME="preference">
<OPTION value = Yankees>Yankees
<OPTION value = Braves>Braves
</SELECT>
<P>
<INPUT TYPE="submit" VALUE="Post Variables">
</FORM>
</TD></TR></TABLE></CENTER>
</BODY>
</HTML>
This file is a regular HTML page with no special qualities other than the
FORM ACTION
that calls a PHP script named phpvaribles.php with a variable passed in the query
string portion of the URL. The query string is any information after the question mark
(
?
); in this case,
ITEM=10
.
The second part of this example is the phpvariables.php script, which prints the
information gathered in the form. The script looks like this:
<?
echo "ITEM = $ITEM <br>";
echo "Email = $email <br>";
echo "Name = $name <br>";
echo "Preference = $preference <br>";
echo "argc = $argc <br>";
echo "argv = $argv[0] <br>";
echo "PHP_SELF = $PHP_SELF <br>";
phpinfo();
?>
This script reads the variables from the PHP environment and prints them out to the
browser. Your results should look something like this:
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ITEM = 10
Email =
Name = Robert Cox
Preference = Braves
argc = 1
argv = ITEM=10
PHP_SELF = /phpbook/phpinfo.php
There should also be additional information at the bottom of this Web page
generated from the phpinfo() function. This function is useful to view the variables
that are available for you to use. For instance, under the Environment section of the
phpinfo()
output, you should see something like the information in Table 2.2
.
(Please note that not all the information output by
phpinfo()
is in this table.)
Table 2.2. PHP Environment Variables Displayed by
phpinfo()
Variable
>Valu
ClassPath
D:\ Program Files\ Exceed.nt \ hcljrcsv.jar;D:\
Program Files\ Exceed.nt\ ;
COMPUTERNAME
PHOENIX
CONTENT_TYPE
application/x-www-form-urlencoded
HTTP_ACCEPT_LANGUAGE en-us
HTTP_HOST
phoenix
HTTP_REFERER
http://phoenix/phpbook /postvars.html
HTTP_USER_AGENT
Mozilla/4.0 (compatible; MSIE 5.01; Windows NT)
HTTP_COOKIE
AAMUILoginName; AAMUILoginPassword;
AAMUILoginLocale
PATH_INFO
/phpbook/phpinfo.php
PATH_TRANSLATED
c:\ InetPub\ wwwroot\ phpbook \ phpinfo.php
QUERY_STRING
ITEM=10
REMOTE_ADDR
172.31.70.107
REMOTE_HOST
172.31.70.107
REQUEST_METHOD
POST
SCRIPT_NAME
/phpbook/phpinfo.php
SERVER_NAME
phoenix
SERVER_PORT
80
SERVER_PORT_SECURE
0
SERVER_PROTOCOL
HTTP/1.1
SERVER_SOFTWARE
Microsoft-IIS/4.0
There is also a section that is output by the
phpinfo()
function that displays PHP
variables. This information differs somewhat from the environment variables detailed
in Table 2.2
. Refer to Table 2.3 for this information.
Table 2.3. PHP Variables Displayed by
phpinfo()
Variable
Value
PHP_SELF
/phpbook/phpinfo.php
HTTP_GET_VARS["ITEM"]
10
HTTP_POST_VARS["name"]
Robert Cox
HTTP_POST_VARS["email"]
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HTTP_POST_VARS["preference"]
Braves
HTTP_SERVER_VARS["PHP_SELF"]
/phpbook/phpinfo.php
HTTP_SERVER_VARS["argv"]
Array ( [0] => ITEM=10 )
HTTP_SERVER_VARS["argc"]
1
Using the Environment to Generate Content
One of the ways that you can vary content to the browser is to use the environment
to dictate what the user sees in the browser. For instance, the information in the
request variables could be used to alter the information that PHP displays. In a
similar manner, the date or time of day could be used to display greetings or other
customized information to the user.
In the following example, the input on the initial page determines what the user's
experience will be on the resulting page. This is a very elementary example, but it
illustrates how the Web page can be modified on-the-fly to tailor content to the user.
<HTML>
<HEAD>
<TITLE></TITLE>
<BODY>
<CENTER>Enter the following information:
<P>
<TABLE width="200"><TR><TD align="left">
<FORM ACTION="result.php" METHOD="POST">
Please select your gender:<BR>
<SELECT NAME="gender">
<OPTION value = Male>Male
<OPTION value = Female>Female
</SELECT>
<P>
<INPUT TYPE="submit" VALUE="Submit">
</FORM>
</TD></TR></TABLE></CENTER>
</BODY>
</HTML>
This is the initial page where the user, through the use of a drop-down list box,
chooses his/her gender. The resulting page will display a pink background if the
chosen gender is female, or blue if the gender is male. The text of the page will also
reflect the choice that is made. Here is the code for the result.php page:
<HTML>
<HEAD>
<TITLE>Result Page</TITLE>
<?
if($gender=="Male"){
$color = "Blue";
}
elseif($gender=="Female"){
$color = "Pink";
}
?>
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<BODY bgcolor=<? echo $color ?>>
<center><b>
<?
if($gender=="Male"){
echo "You selected Male";
}
elseif($gender=="Female"){
echo "You selected Female";
}
?>
</b></center>
</BODY>
</HTML>
This same technique can be used to change the content based on other variables
detailed in Table 2.2
. You can determine what browser a user has and alter the
content accordingly or you could read the time of the PHP server by using the
date()
function and modify the content based on what time the user hits the site. These are
just a few examples of how to use the PHP environment to tailor content to the user.
The limit to this customization is up to you and your imagination.
Working with the Filesystem
Sometimes you might find it necessary to read the host filesystem to determine
rights to directories, to display files, to write to files, or any number of things. PHP
provides many filesystem functions that enable the developer to read, delete, and
modify any number of attributes on directories or files. Please remember that when
using these functions, the Web server oftentimes runs as a specific user with limited
rights. All the filesystem operations discussed will return information based on the
user as which PHP (or the Web server) is running. This means that if you try to
create a file and you don't have the appropriate rights, you will receive an error.
Please keep this in mind as you work with files and directories.
Directory Functions
When working with directory functions such as
readdir()
rewinddir()
, the basic
idea is threefold. First, you must open a directory handle by using the
opendir()
function. This handle is a reference that is used in subsequent directory operations.
Second, you perform operations on the directory. These could be anything from
renaming the directory to changing permissions. Third, you close the directory
handle by using the
closedir()
function. Some directory functions do not require
the use of a directory handle. For functions such as
is_dir()
,
mkdir()
, and
rmdir()
, only the directory name is required. The following example tests for the
existence of the current directory. Of course, this will always return true. You can
change the
$dirname
variable and experiment with what happens if the
is_dir()
function returns false.
<html>
<head>
<title>Testing for a Directory</title>
</head>
<body>
