getting warning while fetching rows from mysql using php - php

Question

It seems to be duplicate question, but I tried all the answers, which has been already posted.
this is my code
include"db.php";
//$poster_id=1;
$sql = "SELECT pi.full_name,pi.poster_img,pi.poster_tag,
p.post_title,p.post_description,p.post_tag,
p.post_snap
FROM POSTS p JOIN POSTER_INFO pi ON p.poster_id=pi.auth_id";
$result = mysql_query($sql) or die(mysql_error());
echo mysql_error();
$msg=" ";
while($row = mysql_fetch_array($result)) {
$msg_footer="<div class='post_footer'>";
$msg_footer=$msg_footer."<div class='post_img'>";
$msg_footer=$msg_footer."<img src='". 'data:image/jpeg;base64,' . base64_encode( $row[6] ) ."' width='330' height='130' /></div>";
$msg_footer=$msg_footer."<div class='post_author'><div class='author_img'><img src='". 'data:image/jpeg;base64,' . base64_encode( $row[1] ) ."' width='80' height='80' /></div>";
$msg_footer=$msg_footer."<div class='author_info'><b>". $row[0] ."</b><br/><span style='font-size:11px'>". $row[2] ."</span><br/><span style='font-size:10px'>1 Post</span></div></div></div>";
$msg .= " <li><br/><span class='post_title'>". $row[3] ."</span><br/><br/><span class='post_description'>" . $row[4] . "</span></li>";
$msg .=$msg_footer; //WARNING POINTING TO THIS LINE
}
I'm getting warning, which pointing last line of while loop;
Warning: mysql_fetch_array() expects parameter 1 to be resource, boolean given in C:\xampp\htdocs\labs\load_data.php on line 40
My sql query is correct, because, I tried to execute it in sql editor and in php page.
like this
<?php
$sql = "SELECT pi.full_name,pi.poster_img,pi.poster_tag,
p.post_title,p.post_description,p.post_tag,
p.post_snap
FROM POSTS p JOIN POSTER_INFO pi ON p.poster_id=pi.auth_id";
$result = mysql_query($sql) or die(mysql_error());
echo mysql_error();
while($row = mysql_fetch_array($result)) {
?>
<tr>
<td><?php echo $row[0]; ?></td>
<td><?php echo $row[2]; ?></td>
<td><?php echo $row[3]; ?></td>
</tr>
<?php }
?>
In this case, I'm not getting any warning.

Answer 1

I'm pretty sure that the error is not triggered by the code that you have posted.
Check the return value of mysql_query() at all positions in the code, like this:
if(mysql_query(...) === FALSE) {
die(mysql_error());
}
I see you are already doing it in the code you have shown, but the warning will be triggered at another point in the code I assume.
Another explanation might be, that you overwrite $result somewhere in the code - but this is not shown as well.
General advice: Don't use mysql_* functions for new code. They are deprecated. Use PDO or mysqli_* instead

Answer 2

I think your query is failing, so producing a boolean FALSE instead of a query resource. But it's very strange that the second one runs fine..