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You create these functions and put them to work step by step in the following exercise.

Building the Link Factory

1.

In your

seophp

folder, create a new folder named

include

.

2.

In the

include

folder, create a file named

config.inc.php

, and add this code to it:

<?php

// site domain; no trailing ‘/‘ !

define(‘SITE_DOMAIN’, ‘http://seophp.example.com’);

?>

3.

Also in the

include

folder, create a file named

url_factory.inc.php

, and add the

_prepare_

url_text()

and

make_product_url()

functions to it as shown in the code listing:

<?php

// include config file

require_once ‘config.inc.php’;

// prepares a string to be included in an URL

function _prepare_url_text($string)

{

// remove all characters that aren’t a-z, 0-9, dash, underscore or space

$NOT_acceptable_characters_regex = ‘#[^-a-zA-Z0-9_ ]#‘;

$string = preg_replace($NOT_acceptable_characters_regex, ‘’, $string);

// remove all leading and trailing spaces

$string = trim($string);

// change all dashes, underscores and spaces to dashes

$string = preg_replace(‘#[-_ ]+#‘, ‘-‘, $string);

// return the modified string

return $string;

}

If you’re a PHP OOP (object-oriented programming) fan, you might like to place these

functions into a class. In this case, the

_prepare_url_text()

function should be a

private method because it’s only intended for internal use, and the

make_product_

url()

would be a public method. OOP features are not used in this chapter to keep

the examples simple and brief, but the underscore character is used to prefix func-

tions that are meant for internal use only — such as in

_prepare_url_text()

— to

make an eventual migration to object-oriented code easier. Later the book uses PHP

OOP features when that is recommended by the specifics of the exercises.

67

Chapter 3: Provocative SE-Friendly URLs

c03.qxd:c03 10:39 67

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