Better way of retrieving info from XML file using XPATH - php

Question

I've got so far a very simple class named Menu.php which contains the following:
<?php
class Menu
{
private $_dom;
private $categoryItems;
function __construct()
{
if(file_exists('Menu.xml'))
{
$this->_dom = simplexml_load_file('Menu.xml');
}
}
public function retrieveMenu($category)
{
$products = $this->_dom->xpath('/menu/category[#name="'.$category.'"]');
return $products;
}
} // end of class Menu
Pretty rudimentary, I know, is just for testing purposes.
Now, I also have a XML file like the following:
<?xml version="1.0" encoding="UTF-8" ?>
<menu>
<category name="pizza">
<item name="Tomato and Cheese">
<type>Regular</type>
<available>true</available>
<size name="Small">
<price>5.50</price>
</size>
<size name="Large">
<price>9.75</price>
</size>
</item>
</category>
<category name="pizza">
<item name="Pepperoni">
<type>Regular</type>
<available>true</available>
<size name="Small">
<price>6.85</price>
</size>
<size name="Large">
<price>10.85</price>
</size>
</item>
</category>
Which goes on with multiple products. So, the idea is to access this file through the class,
and to achieve that I'm doing the following in my index.php:
<?php
require 'Menu.php';
$menu = new Menu();
$tests = $menu->retrieveMenu('pizza');
foreach($tests as $test) {
echo $test->attributes();
echo '<br />';
foreach($test->item as $item) {
echo $item->attributes();
echo '<br />';
echo $item->type;
echo '<br />';
echo $item->available;
echo '<br />';
foreach($item->size as $price) {
echo $price->attributes();
echo '<br />';
echo $price->price;
echo '<br />';
echo '<br />';
echo $price->price;
echo '<br />';*/
}
//echo $item->size->attributes();
echo '<br /><br /><br /><br />';
}
}
Which is given me back the results I'd expect:
>pizza
>Tomato and Cheese
>Regular
>true
>Small
>5.50
>Large
>9.75
Now, my question is: Since I'm using 3 nested for loops if I'm not wrong the complexity is n^3, which is pretty awful, the original XML contains lots of products, is there a better way of accessing it? Am I doing something wrong?
By the way, YES, I MUST USE XML and XPATH

Answer 1

Nothing wrong with the nested loops in this case. You access and output all the sub elements on a single resource. But yes it is possible with Xpath to fetch nodes from different levels into a list.
Xpath expressions can use | to combine several location paths. So its is actually three location paths and the expression returns all of the matching nodes:
name attribute nodes from all elements: //*/#name
child elements of item except size: //item/*[not(self::size)]
price child elements of item/size: //item/size/price
This example uses DOM:
$dom = new DOMDocument();
$dom->loadXml($xml);
$xpath = new DOMXpath($dom);
$expression = '//*/#name|//item/*[not(self::size)]|//item/size/price';
foreach ($xpath->evaluate($expression) as $node) {
echo trim($node->nodeValue), "<br/>\n";
}
Output:
pizza<br/>
Tomato and Cheese<br/>
Regular<br/>
true<br/>
Small<br/>
5.50<br/>
Large<br/>
9.75<br/>
pizza<br/>
Pepperoni<br/>
Regular<br/>
true<br/>
Small<br/>
6.85<br/>
Large<br/>
10.85<br/>
A location path in Xpath works like a filter, the nodes are returned in an order depending on their position in the document.
It works with SimpleXML, too:
$element = simplexml_load_string($xml);
$expression = '//*/#name|//item/*[not(self::size)]|//item/size/price';
foreach ($element->xpath($expression) as $node) {
echo trim($node), "<br/>\n";
}
Demo: https://eval.in/156266