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If

$query string

is

a=1&aff_id=34&b=2

, then the

items

array will have these three elements:

$items[0] => ‘a=1’

$items[1] => ‘aff_id=34’

$items[2] => ‘b=2’

You then parse each of these items using the

foreach,

and you split each item on the

=

character using

explode

. Using the resulting data you build an associative array named

$qs_array

, which is returned at

the end. You use the

urldecode()

function when saving each query string parameter, because special

characters may have been encoded:

// initialize the return array

$qs_array = array();

// create the array

foreach($items as $i)

{

// split the name-value pair and save the elements to $qs_array

$pair = explode(‘=’, $i);

$qs_array[urldecode($pair[0])] = urldecode($pair[1]);

}

// return the array

return $qs_array;

}

We looked at

parse_query_string()

because it’s used by

remove_query_param()

, which is the

function of interest — as you remember, it’s called from

aff_test.php

to remove the

aff_id

parameter

from the query string.

The

remove_query_param()

function receives two parameters: the URL and the parameter you want to

remove from that URL. The URL will be something like

/aff_test.php?a=1&b=2

. Because the query

string is what you need for further processing,

remove_query_param()

starts by splitting the

$url

parameter into an

$url_path

and a

$query_string

:

// removes a parameter from the query string

function remove_query_param($url, $param)

{

// extract the query string from $url

$tokens = explode(‘?’, $url);

$url_path = $tokens[0];

$query_string = $tokens[1];

Next, you use the

parse_query_string()

function to transform the query string into an associative array:

// transform the query string into an associative array

$qs_array = parse_query_string($query_string);

As mentioned earlier, the associative array will be something like this:

‘a’ => ‘1’

‘aff_id’ => ‘34’

‘b’ => ‘2’

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Chapter 5: Duplicate Content

c05.qxd:c05 10:41 116

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