insert variable into href in php not working - php

Question

Been struggling with this for hours. Followed several similar examples I found online, none identical situation, and can't get it to pass the variable. I know it's basic, but just learning. Thanks in advance.
<?php
foreach($arr as $r) {
echo "<tr>";
echo "<td>".$r['TimeStamp']."</td>";
echo "<td>".$r['LocationName']."</td>";
**echo "<td><a href='details_get.php?id='$r['Post_ID']>".$r['Title']."</a></td>";**
echo "<td>".$r['Price']."</td>";
echo "<td>".$r['Description']."</td>";
echo "</tr>";
}
?>
I added a variable $id to make the code clearer and easier to work with, but still can't pass the value.
<?php
foreach($arr as $r) {
$id = $r['Post_ID'];
echo "<tr>";
echo "<td>".$r['TimeStamp']."</td>";
echo "<td>".$r['LocationName']."</td>";
echo "<td><a href='details_get.php?id='.$id.'>".$r['Title']."</a></td>";
echo "<td>".$r['Price']."</td>";
echo "<td>".$r['Description']."</td>";
echo "</tr>";
}
?>
Finally got it to work, but I had to separate my php foreach loop and html as found in this post works.
<?php foreach($arr as $r) : ?>
<tr>
<td><?php echo $r['TimeStamp']; ?></td>
<td><?php echo $r['LocationName']; ?></td>
<td><?php echo $r['Title']; ?></td>
<td><?php echo $r['Price']; ?></td>
<td><?php echo $r['Description']; ?></td>
</tr>
<?php endforeach; ?>

Answer 1

**echo "<td><a href='details_get.php?id='$r['Post_ID']>".$r['Title']."</a></td>";**
this row should look like
echo <td>".$r['Title']."</td>";
You are missing a dot in the $r['Post_ID'] I think.
If you share more information may be I can give you others advises