Unexpected output from xpath screen scraping - php

Question

Despite the xpath being correct (to the best of my knowledge), this code is still outputting strangely.
By this I mean that lots of was_price and now_price values are not being scraped from the page and so are returning as £.
Any idea what's wrong?
Here's the site I'm scraping from.
Code:
function scrape($list_url, $shop_name, $photo_location, $photo_url_root, $product_location, $product_url_root, $was_price_location, $now_price_location, $gender, $country, mysqli $con)
{
$html = file_get_contents($list_url);
$doc = new DOMDocument();
libxml_use_internal_errors(TRUE);
if(!empty($html))
{
$doc->loadHTML($html);
libxml_clear_errors(); // remove errors for yucky html
$xpath = new DOMXPath($doc);
/* FIND LINK TO PRODUCT PAGE */
$products = array();
$row = $xpath->query($product_location);
/* Create an array containing products */
if ($row->length > 0)
{
foreach ($row as $location)
{
$product_urls[] = $product_url_root . $location->getAttribute('href');
}
}
else { echo "product location is wrong<br>";}
$imgs = $xpath->query($photo_location);
/* Create an array containing the image links */
if ($imgs->length > 0)
{
foreach ($imgs as $img)
{
$photo_url[] = $photo_url_root . $img->getAttribute('src');
}
}
else { echo "photo location is wrong<br>";}
$was = $xpath->query($was_price_location);
/* Create an array containing the was price */
if ($was->length > 0)
{
foreach ($was as $price)
{
$stripped = preg_replace("/[^0-9,.]/", "", $price->nodeValue);
$was_price[] = "£".$stripped;
}
}
else { echo "was price location is wrong<br>";}
$now = $xpath->query($now_price_location);
/* Create an array containing the sale price */
if ($now->length > 0)
{
foreach ($now as $price)
{
$stripped = preg_replace("/[^0-9,.]/", "", $price->nodeValue);
$now_price[] = "£".$stripped;
}
}
else { echo "now price location is wrong<br>";}
$result = array();
/* Create an associative array containing all the above values */
foreach ($product_urls as $i => $product_url)
{
$result[] = array(
'product_url' => $product_url,
'shop_name' => $shop_name,
'photo_url' => $photo_url[$i],
'was_price' => $was_price[$i],
'now_price' => $now_price[$i]
);
}
echo json_encode($result);
}
else
{
echo "this is empty";
}
}
$list_url = "http://www.asos.com/Women/Sale/70-Off-Sale/Cat/pgecategory.aspx?cid=16903&pge=0&pgesize=1002&sort=-1";
$shop_name = "ASOS";
$photo_location = "//ul[#id='items']/li/div[#class='categoryImageDiv']/*[1]/img";
$photo_url_root = "";
$product_location = "//ul[#id='items']/li/div[#class='categoryImageDiv']/*[1]";
$product_url_root = "http://www.asos.com";
$was_price_location = "//ul[#id='items']/li/div[#class='productprice']/span[#class='price' or #class='recRP rrp']"; // leave recRP rrp
$now_price_location = "//ul[#id='items']/li/div[#class='productprice']/span[#class='prevPrice previousprice' or #class='price outlet-current-price']"; // leave outlet-current-price
$gender = "f";
$country = "UK";
scrape($list_url, $shop_name, $photo_location, $photo_url_root, $product_location, $product_url_root, $was_price_location, $now_price_location, $gender, $country, $con);

Answer 1

I was counting the number of matches per site, and it looks like that there are 1563 hits for your was_price and only 1440 for your now_price. This tells me that either your Xpath isn't working in 100% of the cases or that some of the articles only have one price.
So you have to make sure that all of our XPath expressions return the same amount of results, so that: products = new_price = old_price = images