Accounting for missing array keys, within PHP foreach loop - php

Question

I'm parsing a document for several different values, with PHP and Xpath. I'm throwing the results/matches of my Xpath queries into an array. So for example, I build my $prices array like this:
$prices = array();
$result = $xpath->query("//div[#class='the-price']");
foreach ($result as $object) {
$prices[] = $object->nodeValue; }
Once I have my array built, I loop through and throw the values into some HTML like this:
$i = 0;
foreach ($links as $link) {
echo <<<EOF
<div class="the-product">
<div class="the-name"><a title="{$names[$i]}" href="{$link}" target="blank">{$names[$i]}</a></div>
<br />
<div class="the-image"><a title="{$names[$i]}" href="{$link}" target="blank"><img src="{$images[$i]}" /></a></div>
<br />
<div class="the-current-price">Price is: <br> {$prices[$i]}</div>
</div>
EOF;
$i++; }
The problem is, some items in the original document that I'm parsing don't have a price, as in, they don't even contain <div class='the-price'>, so my Xpath isn't finding a value, and isn't inserting a value into the $prices array. I end up returning 20 products, and an array which contains only 17 keys/values, leading to Notice: Undefined offset errors all over the place.
So my question is, how can I account for items that are missing key values and throwing off my arrays? Can I insert dummy values into the array for these items? I've tried as many different solutions as I can think of. Mainly, IF statements within my foreach loops, but nothing seems to work.
Thank you

Answer 1

I suggest you look for an element inside your html which is always present in your "price"-loop. After you find this object you start looking for the "price" element, if there is none, you insert an empty string, etc. into your array.

Answer 2

Instead of directly looking for the the-price elements, look for the containing the-product. Loop on those, then do a subquery using those nodes as the starting context. That way you get all of the the-product nodes, plus the prices for those that have them.
e.g.
$products = array();
$products = $xpath->query("//div[#class='the-product']");
$found = 0 ;
foreach ($products as $product) {
$products[$found] = array();
$price = $xpath->query("//div[#class='the-price']", $product);
if ($price->length > 0) {
$products[$found] = $price->item(0)->nodeValue;
}
$found++;
}

Answer 3

If you don't want to show the products that don't have a price attached to them you could check if $prices[$i] is set first.
foreach($links AS $link){
if(isset($prices[$i])){
// echo content
}
}
Or if you wanted to fill it will dummy values you could say
$prices = array_merge($prices,
array_fill(count($prices), count($links)-count($prices),0));
And that would insert 0 as a dummy value for any remaining values. array_fill starts off by taking the first index of the array (so we start one after the amount of keys in $prices), then how many we need to fill, so we subtract how many are in $prices from how many are in $links, then we fill it with the dummy value 0.
Alternatively you could use the same logic in the first example and just apply that by saying:
echo isset($prices[$i]) ? $prices[$i] : '0';

Answer 4

Hard to understand the relation between $links and $prices with the code shown. Since you are building the $prices array without any relation to the $links array, I don't see how you would do this.
Is $links also built via xpath? If so, is 'the-price' div always nested within the DOM element used to populate $links?
If it is you could nest your xpath query to find the price within the query used to find the links and use a counter to match the two.
i.e.
$links_result = $xpath->query('path-to-link')
$i = 0
foreach ($links_result as $link_object) {
$links[$i] = $link_object->nodeValue;
// pass $link_object as context reference to xpath query looking for price
$price_result = $xpath->query('path-to-price-within-link-node', $link_object);
if (false !== $price_result) {
$prices[$i] = $price_result->nodeValue;
} else {
$prices[$i] = 0; // or whatever value you want to show to indicate that no price was available.
}
$i++;
}
Obviously, there could be additional handling in there to verify that only one price value exists per link node and so forth, but that is basic idea.