The PHP Scripting Language - Managing include files (
Page 10 of 10 )
As you develop reusable code, you should consider how you will arrange your include files. By default, when a file is included using the include or require statements, PHP searches for the file in the same directory as the script being executed. You can include files in other directories by specifying a file path in the include or require statements. The following example shows how relative and absolute file paths can be used:
// a relative file pat
h
require "../inc/myFunctions.php";
// an absolute file path
require "/library/database/db.inc";
The paths can be specified with forward slashes for both Unix and Microsoft Win
dows environments, allowing scripts to be moved from one environment to another. However, using paths can make it difficult to change the directory structure of your application.
A more sophisticated, and flexible alternative to accessing include files is to set the
include_path
parameter defined in the php.ini configuration file. One or more directories can be specified in the
include_path
parameter, and when set, PHP will search for include files relative to those directories. The following extract from the php.ini file shows how to set the
include_path
parameter:
;;;;;;;;;;;;;;;;;;;;;;;;;
; Paths and Directories ;
;;;;;;;;;;;;;;;;;;;;;;;;;
; UNIX: "/path1:/path2"
;include_path = ".:/php/includes:/usr/local/php/projectx"
;
; Windows: "\path1;\path2"
include_path = ".;c:\php\includes;d:\php\projectx"
Path specifications for this parameter are system specific. Unix paths use the for
ward slash and are separated with the colon (:) character, while Microsoft Windows paths use the backslash and are separated by semi colons (;).
The php.ini configuration file defines many parameters that are used to define aspects of PHP’s behavior. Whenever you change php.ini, you need to restart your Apache web server so that the changes are re-read; instructions for restarting are in Appendix A.
If you set the
include_path
parameter,
include
and
require
directives need only specify a path relative to a directory listed in the
include_path
. For example, if the
include_path
is set to point at /usr/local/php/projectx, and you have an include file security.inc that’s stored in /usr/local/php/projectx/security, you only need to add:
include "security/security.inc";
to your script file. The PHP engine will check the directory /usr/local/php/projectx, and locate the subdirectory security and its include file. Include files that are placed in directories outside of the web server’s document root are protected from accessed via the web server. In Chapter 6 we describe how to protect include files that are under the web server root directory.
For a large project, you might place the project-specific code into one directory, while keeping reusable code in another; this is the approach we use in our case study, Hugh and Dave’s Online Wines, as we describe in Chapter 15.
A Working Example
In this section, we use some of the techniques described so far to develop a simple, complete PHP script. The script doesn’t process input from the user, so we leave some of the best features of PHP as a web scripting language for discussion in later chapters.
Our example is a script that produces a web page containing the times tables. Our aim is to output the 1–12 times tables. The first table is shown in Figure 2-2 as rendered by a Mozilla browser.
Figure 2-2. The output of the times-tables script rendered in a Mozilla browser
The completed PHP script and HTML to produce the times tables are shown in Example 2-4. The first ten lines are the HTML markup that produces the
<head>
components and the
<h1> The Times Tables</h1>
heading at the top of the web page. Similarly, the last two lines are HTML that finishes the document:
</body>
and
</html>
.
Between the two HTML fragments that start and end the document is a PHP script to produce the times-table content and its associated HTML. The script begins with the PHP open tag
<?php
and finishes with the close tag
?>
.
Example 2-4. A script to produce the times tables
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
http://www.w3.org/TR/html401/loose.dtd> <html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=iso-8859-1">
<title>The Times-Tables</title>
</head>
<body bgcolor="#ffffff">
<h1>The Times Tables</h1>
<?php
// Go through each table
for($table=1; $table<13; $table++)
{
print "<p><b>The " . $table . " Times Table</b>\n";
// Produce 12 lines for each table
for($counter=1; $counter<13; $counter++)
{
$answer = $table * $counter;
// Is this an even-number counter?
if ($counter % 2 == 0)
// Yes, so print this line in bold
print "<br><b>$counter x $table = " .
"$answer</b>";
else
// No, so print this in normal face
print "<br>$counter x $table = $answer";
}
}
?>
</body>
</html>
The script is designed to process each times table and, for each table, to produce a heading and 12 lines. To do this, the script consists of two nested loops: an outer and inner
for
loop.
The outer
for
loop uses the integer variable
$table
, incrementing it by 1 each time the loop body is executed until
$table
is greater than 12. The body of the outer loop prints the heading and executes the inner loop that actually produces the body of each times table.
The inner loop uses the integer variable
$counter
to generate the lines of the times tables. Inside the loop body, the
$answer
to the current line is calculated by multiplying the current value of
$table
by the current value of
$counter
.
Every second line of the tables and the times-table headings are encapsulated in the bold tag
<b>
and bold end tag
</b>
, which produces alternating bold lines in the resulting HTML output. After calculating the
$answer
,an
if
statement follows that decides whether the line should be output in bold tags. The expression the
if
statement tests uses the modulo operator
%
to test if
$counter
is an odd or even number.
The modulo operation divides the variable
$counter
by 2 and returns the remainder. So, for example, if
$counter
is 6, the returned value is 0, because 6 divided by 2 is exactly 3 with no remainder. If
$counter
is 11, the returned value is 1, because 11 divided by 2 is 5 with a remainder of 1. If
$counter
is even, the conditional expression:
($counter % 2 == 0)
is
true
, and bold tags are printed.
Example 2-4 is complete but not especially interesting. Regardless of how many times the script is executed, the result is the same web page. In practice, you might consider running the script once, capturing the output, and saving it to a static HTML file. If you save the output as HTML, the user can retrieve the same page, with less web-server load and a faster response time.
In later chapters, we develop scripts with output that can change from run to run, and can’t be represented in a static file. In Chapter 6, we show scripts that interact with the MySQL database management system; the result is dynamic pages that change if the underlying data in the database is updated. We also show scripts that interact with the system environment and with user input from fill-in forms.
