RSS到HTML，具有不同数量的元素

Question

I've adapted the code found here http://www.w3schools.com/php/php_ajax_rss_reader.asp to turn XML into HTML, and it works fine.

But what I'm stuck on is getting it to show all the items in a feed when the feed can have varying numbers of items. The feed is published daily and can have anywhere from 12-20 articles in it, and I want to show all of them.

In the For Loop for ($i=0; $i<=12; $i++) if I set the condition to be greater than the number of articles, I get an error PHP Fatal error: Call to a member function getElementsByTagName(), so I can't just set it to a big number.

I get the same error if I just remove the condition.

I can't figure out how to count the number of items, either; if I could do that the solution would be easy.

The feed is created in-house so I could ask my colleague to insert the number of items in the feed; is that the best way to go about it?

Thanks!

Answer 1

If you don't know the number of items in the feed, you can go through them all using a foreach loop. Here is an example using the RSS feed from the PHP tag on StackOverflow. Have a look at the rss format so you can see what each entry looks like, and compare it to the code below.

# start off like the w3schools code...
$xml=("https://stackoverflow.com/feeds/tag?tagnames=php&sort=newest");

$xmlDoc = new DOMDocument();
$xmlDoc->load($xml);

# StackOverflow uses the <entry> element for each separate item.
# find all the "entry" items. This returns an array of matching entry elements
$items = $xmlDoc->getElementsByTagName('entry');

# go through the array of "entry" elements one at a time
# $items is the array of <entry> elements
# $i is set to each <entry> in turn, starting from the first one on the page
foreach ($items as $i) {

    # some sample code to get the title, tags, and link
    $title = $i->getElementsByTagName('title')->item(0)->nodeValue;
    $href = $i->getElementsByTagName('link')->item(0)->getAttribute('href');
    $tags = $i->getElementsByTagName('category');
    $tag_arr = [];
    foreach ($tags as $t) {
        $tag_arr[] = $t->getAttribute('term');
    }
    echo "Title: $item_title; tags: " . implode(", ", $tag_arr) . ";
href: $href

";
}

Using a foreach loop means you are not stuck with having to work out how many items you have in your array, and you don't have to set up an array iterator using for ($i = 0; $i < 500; $i++).