PHP and MySQL Web Development 4th Ed-tqw-_darksiderg

838 Chapter 33 Connecting to Web Services with XML and SOAP
Using REST to Make a Request and Retrieve a Result
With the set of class member variables already set at the beginning of the
browseNodeSearch() function (or ASINSearch() or keywordSearch()), all that remains
for using REST/XML over HTTP is to format and send the URL:
$this->url = "http://ecs.amazonaws.com/onca/xml?".
"Service=".$this->Service.
"&Operation=".$this->Operation.
"&AssociateTag=".$this->AssociateTag.
"&AWSAccessKeyId=".$this->AWSAccessKeyId.
"&BrowseNode=".$this->BrowseNode.
"&ResponseGroup=".$this->ResponseGroup.
"&SearchIndex=".$this->SearchIndex.
"&Sort=".$this->Sort.
"&TotalPages=".$this->TotalPages;
The base URL in this case is http://ecs.amazonaws.com/onca/xml.To this, you append
the variable names and their values to form a GET query string. Complete documentation
on these and other possible variables can be found in the AWS Developer’s Guide.
After you set all these parameters, you call
$this->parseXML();
to actually do the work.The parseXML() method is shown in Listing 33.10.
Listing 33.10
parseXML() Method—Parsing the XML Returned from a Query
// Parse the XML into Product object(s)
function parseXML() {
// suppress errors because this will fail sometimes
$xml = @simplexml_load_file($this->url);
if(!$xml) {
//try a second time in case just server busy
$xml = @simplexml_load_file($this->url);
if(!$xml) {
return false;
}
}
$this->totalResults = (integer)$xml->TotalResults;
foreach($xml->Items->Item as $productXML) {
$this->products[] = new Product($productXML);
}
The function simplexml_load_file() does most of the work for you. It reads in the
XML content from a file or, in this case, an URL. It provides an object-oriented interface
to the data and the structure in the XML document.This is a useful interface to the