Sort PHP - 2 columns with common subheaders - php

Question

My code does the two columns, like this:
neighborhood 1
restaurant 1
neighborhood 1
restaurant 2
neighborhood 1
restaurant 3
I WANT:
neighborhood 1
restaurant 1
restaurant 2
restaurant 3
$result = mysql_query("SELECT ID,RName,NHood FROM Restaurants ORDER BY NHood ASC, TRIM(LEADING 'The ' FROM RName) ASC",$connect);
$numRows = mysql_num_rows($result);
$middleIndex = (int)(($numRows+1) / 2);
$names = array();
while($row = mysql_fetch_assoc($result)) {
$names[] = $row['RName'];
$id[] = $row['ID'];
$hood[] = $row['NHood'];
}
// print the left column
echo "<table>";
echo "<tr>";
echo "<td width=60%>";
echo "<div id=\"left\">\n";
for($i = 0; $i < $middleIndex; $i++) {
echo $hood[$i];
echo "<p>$names[$i]</p>\n";
}
echo "</div>\n";
echo "</td>";
// print the right column
echo "<td>";
echo "<div id=\"right\">\n";
for($i = $middleIndex; $i < $numRows; $i++) {
echo $hood[$i];
echo "<p>$names[$i]</p>\n";
}
echo "</div>\n";
echo "</tr>";
echo "</table>";

Answer 1

Here's the logic you want (pseduocode):
SELECT
ID,
RName,
NHood
FROM
Restaurants
ORDER BY
NHood ASC, RName ASC
This should return a list of results ordered first by the neighborhood, then by restaurant name.
Next, you'll process those results line-by-line to create a nested array with the data structure you want for your view:
$neighborhoods = array();
foreach($result as $row)
{
// Add each restaurant to a list named for the current neighborhood
$neighborhoods[$row['NHood']][] = $row['RName'];
}
This will produce a data structure like this:
$neighborhoods = array(
'neighborhood1' => array(
'restaurant1',
'restaurant2',
'restaurant3',
),
'neighborhood2' => array(
'restaurant1',
'restaurant2',
),
)
Which you will then use by doing this:
foreach($neighborhoods as $neighborhood => $restaurants)
{
echo $neighborhood;
foreach($restaurants as $restaurant)
{
echo $restaurant;
}
}
If your list is really large and you're worried about memory the implementation is a bit different but the logic is the same. This technique is faster but it's a bit harder to read and maintain because presentation and data layer logic are all mixed together:
$currentNH = null;
while($row = fetch_row($results))
{
// Detect when the neighborhood changes
if($currentNH != $row['NHood']) {
echo $row['NHood'];
}
echo $row['RName'];
}