print recursive list in php - php

Question

I am trying to print a recursive list where every date has a sublist of events ordered by date.
For example on the database I have:
+------+----------+--------+
| date | event_id | post_id|
+------+----------+--------+
|date1 | event1 | post1 |
|date1 | event2 | post2 |
|date1 | event3 | post3 |
|date2 | event4 | post4 |
|date2 | event5 | post5 |
+------+----------+--------+
I need to print
<ul>
<li>date1</li>
<ul>
<li>event1, post1</li>
<li>event2, post2</li>
<li>event3, post3</li>
</ul>
<li>Date 2</li>
<ul>
<li>event4, post4</li>
<li>event5, post5</li>
</ul>
</ul>
how can I print in php the
select date, event_id, post_id from tablename
query in php to have this?

Answer 1

After a while with php and mysql, I do the least I can in mysql, even if it's often more elegant. Performance of mysql is crap. And even if what you query is fast, it can still slow down another query elsewhere done by another user. So here is a response with the least load on the DB. One query, no grouping. just select your 3 fields, and you can apply this.
$lastDate = null; // lastDate will be updated at each row, so we can check if it has changed the next one.
echo '<ul>';
foreach ($queryResult as $row)
{
if ( $lastDate != $row['date'] )
{
if ( $lastDate) { echo '</ul>'; } // if lastdate "exists", it's not the first, so let't close the "date" list...
echo '<li>', $row['date'], '</li><ul>'; // ... and start a new one
}
echo '<li>', $row['event_id'], ', ',$row['post_id'], '</li>';
$lastDate = $row['date'];
}
echo '</ul>'; // close the very last date list
echo '</ul>'; // close the the full list

Answer 2

It looks like you need MySQL GROUP_CONCAT().
SELECT date,
GROUP_CONCAT(event_id) AS 'event_ids',
GROUP_CONCAT(post_id) AS 'post_ids'
FROM tablename
GROUP BY date
This will return results with three fields. date will be the date field, event_ids and post_ids will be comma separated lists of the events and posts that fall under that date.

Answer 3

This should work. You'd want to add some error checking though.
<ul>
<?php
$result = mysql_query(SELECT date FROM tableName);
if (mysql_num_rows($result) > 0)
{
while ($dateRow = mysql_fetch_array($result))
{
echo "<li>" . $dateRow['date'] . "</li>";
$result2 = mysql_query("SELECT event_id,post_id FROM tableName where date = '" . $dateRow['date'] . "'");
if (mysql_num_row($result2) > 0)
{
echo "<ul>";
while ($row = mysql_fetch_array($result2))
{
echo "<li>" . $row['event_id'] . " , " . $row['post_id'] . "</li>";
}
echo "</ul>";
}
}
}
?>
</ul>

Answer 4

The following is a rough answer:
$query = "select date, event_id, post_id from tablename order by date";
$result = mysql_query($query);
$currentDate = null;
echo "<ul>";
while($row = mysql_fetch_assoc($result)){
if($currentDate != $row['date']){
echo "<li>" . $currentDate . "</li>";
echo "<ul>";
}
echo "<li>" . $row['event'] . $row['post'] . "</li>";
if($currentDate != $row['date']){
$currentDate = $row['date'];
echo "</ul>";
}
}
echo "</ul>";

Answer 5

Here's my take on the problem. First of all, you should nest the unordered list items into parent elements. The resulting output should be
<ul>
<li>date1
<ul>
<li>event1, post1</li>
<li>event2, post2</li>
<li>event3, post3</li>
</ul>
</li>
<li>Date 2
<ul>
<li>event4, post4</li>
<li>event5, post5</li>
</ul>
</li>
</ul>
Advantages of this nested schema:
valid html (this alone is good enough)
easier DOM-manipulation by Javascript
Here's a function which in theory should output the former html:
function printList()
{
$sql = 'SELECT t.event_id, t.post_id, t.date FROM table t ORDER BY date';
$result = mysql_query($sql);
$date = null;
$out = '';
while($row = mysql_fetch_assoc($result))
{
if($date !== $row['date'])
{
if(!is_null($date))
{
$out .= '</ul></li>';
}
$date = $row['date'];
$out .= sprintf('<li>%s<ul>', $row['date']);
}
$out.= sprintf('<li>%s, %s</li>', $row['event_id'], $row['post_id']);
}
return sprintf('<ul>%s</ul></li></ul>', $out);
}

Answer 6

$sql = "SELECT date, event_id, post_id
FROM tablename
GROUP BY date ORDER BY date";