Distinguish between elements and last element of array - php

Question

Im creating tablerows based on the number of the array colours:
$query = mysql_query("SELECT * FROM things);
$num = mysql_num_rows($query );
$colours = array ();
if($num)
{
for ($i = 0; ($row = mysql_fetch_assoc($query)); ++$i)
{
$colours[$i] = $row["colours"];
}
}
$arrlength = count($colours);
for ($i = 0; ($i < ($arrlength)); ++$i){
echo "
<tr class='border_bottom'><td>".$colours[$i]."</td></tr>
";
}
So, if colours is, lets say, equal to 8, 8 table rows with the class border_bottom are created.
border_bottom is used by CSS to add a border to the bottom of each tablerow.
What I need is some PHP help: I need code which checks the array colours. The last element of the array has to go with an empty id since I dont want a border-bottom added to that very last tablerow. All other tablerows have to go with the border_bottom class, tho.
I was thinking of starting the code like that:
echo"
<tr class='
";
-->PHP code goes here<--
echo"
'>
<td>".$colours[$i]."</td></tr>

Answer 1

Try this:
<?php
$query = mysql_query("SELECT * FROM things");
$num = mysql_num_rows($query);
$colours = array();
if($num)
{
while($row = mysql_fetch_assoc($query))
{
$colours[] = $row["colours"];
}
}
$arrlength = count($colours);
for ($i = 0; $i < $arrlength; ++$i){
if($i < $arrlength - 1){
echo "<tr class='border_bottom'><td>{$colours[$i]}</td></tr>";
}else{
echo "<tr><td>{$someColor}</td></tr>";
}
}

Answer 2

Try the following code in your table row echo
echo "<tr"
.($i < $arrlength - 1 ? " class='border_bottom'" : "")
.">"
."<td>{$colours[$i]}</td></tr>";

Answer 3

You can actually do this while fetching the rows without needing to count how many there are, by reading ahead one row.
$previous_row = mysql_fetch_array(); // fetch the first row (if there is one)
while ($previous_row) {
if ($row = mysql_fetch_array()) {
// if another row is fetched, then the previous row was NOT the last row
echo '<tr class="border_bottom"><td>' . $previous_row['colours'] . '</td></tr>';
} else {
// otherwise, the previous row WAS the last row, and does not get the class
echo '<tr><td>' . $previous_row['colours'] . '</td></tr>';
}
$previous_row = $row; // Set the previous row to the current row
}