Loop results executing twice - php

Question

I creating a simple site with PHP where the users can submit blogs and other users (who are logged in) can post comments on them. I have made a link called "comments" below each blog that when clicked will show / hide all the comments relevant to the specific blog (also if the user is logged in, it will show a form field in which they can submit new comments). So basically each blog will have multiple comments. I have done two different codes for this but they both have the same problem that each comment appears twice (everything else works fine). Could anyone point out why?
mysql_select_db ("ooze");
$result = mysql_query ("select * from blog") or die(mysql_error());
$i = 1;
while($row = mysql_fetch_array($result))
{
echo "<h1>$row[title]</h1>";
echo "<p class ='second'>$row[blog_content]</p> ";
echo "<p class='meta'>Posted by .... • $row[date] • Comments<div id='something$i' style='display: none;'>";
$i++;
$a = $row["ID"];
$result2 = mysql_query ("select * from blog, blogcomment where $a=blogID") or die(mysql_error());
while($sub = mysql_fetch_array($result2))
{
echo "<p class='third' >$sub[commentdate] • $sub[username]</p><p>said:</p> <p>$sub[comment]</p>";
}
if ( isset ($_SESSION["gatekeeper"]))
{
echo '<form method="post" name="result_'.$row["ID"].'" action="postcomment.php"><input name="ID" type = "hidden" value = "'.$row["ID"].'" /><input name="comment" id="comment" type="text" style="margin-left:20px;"/><input type="submit" value="Add comment" /></form>';
}
else
{
echo '<p class="third">Signup to post a comment</p>';
}
echo "</div>";
}
mysql_close($conn);
//second version of inner loop://
if ( isset ($_SESSION["gatekeeper"]))
{
while($sub = mysql_fetch_array($result2))
{
echo "<p class='third' >$sub[commentdate] • $sub[username] said:</p> <p>$sub[comment]</p>";
}
echo '<form method="post" name="result_'.$row["ID"].'" action="postcomment.php"><input name="ID" type = "hidden" value = "'.$row["ID"].'" /><input name="comment" id="comment" type="text" style="margin-left:20px;"/><input type="submit" value="Add comment" /></form>';
}
else
{
while($sub = mysql_fetch_array($result2))
{
echo "<p class='third' >$sub[commentdate] • $sub[username] said:</p> <p>$sub[comment]</p>";
}
echo '<p class="third">Signup to post a comment</p>';
}
echo "</div>";
}
mysql_close($conn);

Answer 1

Your problem lies in this query from the first example.
$result2 = mysql_query ("select * from blog, blogcomment where $a=blogID")
You have already queried the blog table so there is no need to query it again. Simply changing this to
$result2 = mysql_query ("select * from blogcomment where $a=blogID")
should solve the problem.
However there are many things you need to think about.
Why are you re-inventing the wheel? There are plenty of good blog applications out there. You'd be better off using one of them.
It's not recommended to use the mysql_ family of functions any more. Go away and learn mysqli_ or better still PDO.
You should learn about separation of concerns. At the very least you should make sure your data access/business logic is separate from your display logic. MVC is very common in PHP.
You should also learn about JOINs. Even in this simple inline script you have a query within a loop which is not very efficient. You can combine your queries into one (as you've tried with the inner query). The difference is the one query should be outside your main loop.