Show each date only once - php

Question

All right, this must be an absolutely easy question, and I apologize for that.
I also apologize if I simply failed in finding the right search terms to use to come to an answer on my own. I did try, but my lack of fluency in PHP kind of makes me suck at searching.
I'm looking for a simple way to show each date only once within a foreach loop. I'm looping through data like so:
<?php
echo "<ul>";
foreach($rss_items as $i){
if($i->get_feed()->get_title() == 'Twitter (no # replies)'){
echo "<li>";
echo $i->get_date();
echo "<a href='" .$i->get_link()."'>Twitter</a>";
echo $i->get_title();
echo "</li>";
}
elseif($i->get_feed()->get_title() == 'Pinboard (jpcody)'){
echo "<li>";
echo $i->get_date();
echo "<a href='" .$i->get_link()."'>Pinboard</a>";
echo $i->get_title();
echo "</li>";
}
elseif($i->get_feed()->get_title() == 'Entries at Church Marketing Sucks by Joshua Cody'){
echo "<li>";
echo $i->get_date();
echo "<a href='" .$i->get_link()."'>Church Marketing Sucks</a>";
echo "<a href='" .$i->get_link()."'>" . $i->get_title() . "</a>";
echo $i->get_description();
echo "</li>";
}
elseif($i->get_feed()->get_title() == 'Flickr remove first paragraph'){
echo "<li>";
echo $i->get_date();
echo "<a href='" .$i->get_link()."'>Flickr</a>";
echo "<a href='" .$i->get_link()."'>" . $i->get_title() . "</a>";
echo $i->get_description();
echo "</li>";
}
}
echo "</ul>";
?>
And each item contains the date, so I'm getting the same date multiple times. I'd like to only have each date shown once, a la http://daringfireball.net.
I'm using CodeIgniter and the SimplePie library, so all of the data is being pulled directly instead of being stored in a db. I imagine a way to do it could be including a second if statement to check if the date has already been used, but I don't know how to execute this.
I'm pretty new to PHP, and I'm really looking to learn more than just have a solution given.
Any help you could give would be great!

Answer 1

You need to remember what was the date you used last, and print it only if it differs. You can try something like:
$previous_date = null;
foreach ($rss_items as $item) {
if ($item->get_date() != $previous_date) {
$previous_date = $item->get_date();
echo '<li>' . $previous_date . '</li>';
}
...
}
(And don't forget to HTML-encode the titles and links using htmlspecialchars.)

Answer 2

Do you mean you only want the date to be shown once, before the loop, or once per loop so that it looks like:
Date 1
- item 1
- item 2
- etc...
Date 2
- item 1
- item 2
- etc...
Could you clarify the format? Cause at the moment the date should be shown once for each $i that is valid.