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MAGPIERSS RECIPES: Cooking with Corbies
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"Four and twenty blackbirds baked in a pie."
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1. LIMIT THE NUMBER OF HEADLINES(AKA ITEMS) RETURNED.
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PROBLEM:
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You want to display the 10 (or 3) most recent headlines, but the RSS feed
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contains 15.
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SOLUTION:
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$num_items = 10;
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$rss = fetch_rss($url);
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$items = array_slice($rss->items, 0, $num_items);
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DISCUSSION:
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Rather then trying to limit the number of items Magpie parses, a much simpler,
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and more flexible approach is to take a "slice" of the array of items. And
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array_slice() is smart enough to do the right thing if the feed has less items
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then $num_items.
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See: http://www.php.net/array_slice
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2. DISPLAY A CUSTOM ERROR MESSAGE IF SOMETHING GOES WRONG
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PROBLEM:
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You don't want Magpie's error messages showing up if something goes wrong.
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SOLUTION:
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# Magpie throws USER_WARNINGS only
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# so you can cloak these, by only showing ERRORs
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error_reporting(E_ERROR);
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# check the return value of fetch_rss()
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$rss = fetch_rss($url);
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if ( $rss ) {
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...display rss feed...
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}
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else {
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echo "An error occured! " .
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"Consider donating more $$$ for restoration of services." .
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"<br>Error Message: " . magpie_error();
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}
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DISCUSSION:
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MagpieRSS triggers a warning in a number of circumstances. The 2 most common
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circumstances are: if the specified RSS file isn't properly formed (usually
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because it includes illegal HTML), or if Magpie can't download the remote RSS
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file, and there is no cached version.
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If you don't want your users to see these warnings change your error_reporting
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settings to only display ERRORs. Another option is to turn off display_error,
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so that WARNINGs, and NOTICEs still go to the error_log but not to the webpages.
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You can do this with:
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ini_set('display_errors', 0);
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See: http://www.php.net/error_reporting,
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http://www.php.net/ini_set,
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http://www.php.net/manual/en/ref.errorfunc.php
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3. GENERATE A NEW RSS FEED
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PROBLEM:
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Create an RSS feed for other people to use.
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SOLUTION:
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Use Useful Inc's RSSWriter (http://usefulinc.com/rss/rsswriter/)
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DISCUSSION:
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An example of turning a Magpie parsed RSS object back into an RSS file is forth
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coming. In the meantime RSSWriter has great documentation.
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4. DISPLAY HEADLINES MORE RECENT THEN X DATE
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PROBLEM:
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You only want to display headlines that were published on, or after a certain
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date.
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SOLUTION:
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require 'rss_utils.inc';
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# get all headlines published today
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$today = getdate();
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# today, 12AM
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$date = mktime(0,0,0,$today['mon'], $today['mday'], $today['year']);
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$rss = fetch_rss($url);
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foreach ( $rss->items as $item ) {
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$published = parse_w3cdtf($item['dc']['date']);
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if ( $published >= $date ) {
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echo "Title: " . $item['title'];
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echo "Published: " . date("h:i:s A", $published);
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echo "<p>";
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}
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}
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DISCUSSION:
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This recipe only works for RSS 1.0 feeds that include the <dc:date> field.
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(which is very good RSS style)
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parse_w3cdtf is defined in rss_utils.inc, and parses RSS style dates into Unix
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epoch seconds.
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See: http://www.php.net/manual/en/ref.datetime.php
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