How to read and display one:many tables in PHP? - php

Question

I am trying to combine two things which are already know how to do, but can't figure out how to combine them. Here is what I want to achieve:
I have a database with locations and events. There are several events in each location. I will be using PHP to query the database and output the code needed to display search results. I want something similar to the below:
<div id="location">
<p>Location1</p>
<div id="event">Event1</div>
<div id="event">Event2</div>
<div id="event">Event3</div>
</div>
<div id="location">
<p>Location2</p>
<div id="event">Event4</div>
<div id="event">Event5</div>
<div id="event">Event6</div>
</div>
I know that I can use select distinct to get the unique value of each location, and know that I can use a normal select statement to get all the events, however how do add all the events inside the location div?
My current PHP looks like this:
$sql ="SELECT location, event from events";
$res = mysql_query($sql) or die(mysql_error());
while($row = mysql_fetch_assoc($res)){
$location = $row['location'];
$event = $row['event'];
echo "<div id="location">
<p>$location</p>
<div id="event">$event</div>
</div>";
}
My current code adds duplicates of the same location with 1 unique event in each. Even if I use select distinct I get the same results. How do I group the events have have the same location?

Answer 1

I think you should write something like:
$sql ="SELECT location, event from events";
$res = mysql_query($sql) or die(mysql_error());
$prevlocation = "";
while($row = mysql_fetch_assoc($res))
{
$location = $row['location'];
$event = $row['event'];
if ( $prevlocation != "" ) // Close previous div if needed
{
echo "</div>";
}
if ( $location != $prevlocation )
{
echo "<div id='location'><p>$location</p>";
$prevlocation = $location;
}
else
{
echo "<div id='event'>$event</div>";
}
}
echo "</div>"; // Close last div

Answer 2

If you have join of two tables, let's assume that your query looks like this:
$sql ="SELECT * FROM events
JOIN locations ON
locations.id=events.loc_id";
And then, within one loop, get events and location arrays:
$res = mysql_query($sql) or die(mysql_error());
$locations = array();
$events= array();
while($row = mysql_fetch_assoc($res))
{
$location = $row['location'];
$event = $row['event'];
$loc_id=$row['loc_id'];
$id=$row['id'];
$events[]=$loc_id.'%'.$event;
if(!in_array($id.'%'.$location,$locations)) { // avoid duplicate entries
$locations[]=$id.'%'.$location;
}
}
And, another loop (+loop inside loop):
for($i=0;$i<count($locations);$i++) {
$location=explode('%',$locations[$i]);
echo "<div class='location'>\n
<p>$location[1]</p>\n";
for($j=0;$j<count($events);$j++) {
$event=explode('%',$events[$j]);
if($event[0]==$locations[$i][0]) {
echo "<div class='event'>".$event[1]."</div>";
}
}
echo "</div>";
}
Not so elegant, but it is working, and produces valid HTML. :)
First, i wanted to make two associative arrays, and to compare keys, but i couldn't, because i couldn't convert ID keys to strings, so i made it with explode (% is separator between key and value).