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PHP Amazon Web Services Class


This class, written by Dennis Pallett, is used to query Amazon Web Services (a developers' token is required), and retrieve results from Amazon. The class includes automatic caching for increased stability and speed of your website.

php
###################################################################################
#
# AWS Class, by Dennis Pallett, version 0.1
# http://www.nocertainty.com/e/aws-class
#
# Modified version of XML Library, by Keith Devens included
# See http://keithdevens.com/software/phpxml for a regular version
#
# This code is Open Source, released under terms similar to the Artistic License.
# Read the license at http://keithdevens.com/software/license
###################################################################################

class AWS {
var
$parser;#a reference to the XML parser
var $document; #the entire XML structure built up so far
var $parent;#a pointer to the current parent - the parent will be an array
var $stack;#a stack of the most recent parent at each nesting level
var $last_opened_tag; #keeps track of the last tag opened.
var $token; # AWS Developer Token
var $associateid; # Amazon Associate ID
var $directory; # Directory where all cached XML files should be stored
var $error; # Contains error messages, if any

// Constructor:
function AWS($Token, $AssociateID="aspit-20"){
$this->token = $Token;
$this->associateid = $AssociateID;
}

function
go ($url) {
// Insert associate id and dev token in string
$url = str_replace("[devtoken]", $this->token, $url);
$url = str_replace ("[associateid]", $this->associateid, $url);


// Create cached filename
$cachefn = md5($url);
$cachefn .= ".xml";
$cachefn = $this->directory . $cachefn;

// Does a cached file exist?
if (file_exists ($cachefn)) {
// Get last modified time
$cachetime = filemtime($cachefn);

// Cache too old?
if ($cachetime > mktime() - 60*60*24) {
// Get xml from local cache
$xml = implode(" ", file($cachefn));
}
}

// Check if there is any xml from local copy
if (empty($xml)) {
// Doesn't exist yet or too old, get xml from AWS
$xml = implode(" ", file($url));
}

// Parse xml into array
$data = &$this->parse($xml);

// Destroy XML parser
$this->destruct();

// Get the product info
$data = $data['ProductInfo'];

// Check for error message
if (!empty($data['ErrorMsg'])) {
// Get old cache copy, if any
if (file_exists ($cachefn)) {
// Get xml from local cache
$xml = implode(" ", file($cachefn));
} else {
// No cache, just return false and set error message
$this->error = $data['ErrorMsg'];
return
false;
}
}

// Write local cache copy
$f = fopen($cachefn, "w");
fwrite($f, $xml);
fclose($f);

return
$data;
}

function
destruct(){ xml_parser_free(&$this->parser); }

function &
parse(&$data){
$this->parser = &xml_parser_create();
xml_parser_set_option(&$this->parser, XML_OPTION_CASE_FOLDING, false);
xml_set_object(&$this->parser, &$this);
xml_set_element_handler(&$this->parser, 'open','close');
xml_set_character_data_handler(&$this->parser, 'data');

$this->document = array();
$this->stack= array();
$this->parent= &$this->document;
return
xml_parse(&$this->parser, &$data, true) ? $this->document : NULL;
}
function
open(&$parser, $tag, $attributes){
$this->data = ''; #stores temporary cdata
$this->last_opened_tag = $tag;
if(
is_array($this->parent) and array_key_exists($tag,$this->parent)){ #if you've seen this tag before
if(is_array($this->parent[$tag]) and array_key_exists(0,$this->parent[$tag])){ #if the keys are numeric
#this is the third or later instance of $tag we've come across
$key = count_numeric_items($this->parent[$tag]);
}else{
#this is the second instance of $tag that we've seen. shift around
if(array_key_exists("$tag attr",$this->parent)){
$arr = array('0 attr'=>&$this->parent["$tag attr"], &$this->parent[$tag]);
unset(
$this->parent["$tag attr"]);
}else{
$arr = array(&$this->parent[$tag]);
}
$this->parent[$tag] = &$arr;
$key = 1;
}
$this->parent = &$this->parent[$tag];
}else{
$key = $tag;
}

// If only URL attribute, add url to main array
// Else, add attributes to seperate array
if (count($attributes) == 1 AND !empty($attributes['url'])) {
$this->parent[$key]['url'] = $attributes['url'];
} elseif (
$attributes) {
$this->parent["$key attr"] = $attributes;
}


$this->parent= &$this->parent[$key];
$this->stack[]= &$this->parent;
}
function
data(&$parser, $data){
if(
$this->last_opened_tag != NULL) #you don't need to store whitespace in between tags
$this->data .= $data;
}
function
close(&$parser, $tag){
if(
$this->last_opened_tag == $tag){
$this->parent = $this->data;
$this->last_opened_tag = NULL;
}
array_pop($this->stack);
if(
$this->stack) $this->parent = &$this->stack[count($this->stack)-1];
}
}

function
count_numeric_items(&$array){
return
is_array($array) ? count(array_filter(array_keys($array), 'is_numeric')) : 0;
}

// Use this class like this:

// Include AWS Class
include ("aws.php")

// Create new instance of AWS class, inputing the developer token and associate id
$aws = &new AWS("[Dev Token Goes Here]", "aspit-20");

// Set cache directory
$aws->directory = "/home/you/cache/";

// Get AWS data
// [associateid] and [devtoken] are automatically replaced by their values
$data = $aws->go ("http://xml.amazon.com/onca/xml3?t=[associateid]&dev-t=[devtoken]&AsinSearch=0439139597&type=lite&f=xml");

// Do something with the data here
// ...
?>
About the author
Dennis Pallett is the main contributor to PHPit. He owns several websites, including ASPit and Chill2Music. He is currently still studying.

Dennis Pallett has written 5 tutorials, 2 FAQs, and 19 codesnippets.