It says the error is in the while loop.
<?php
$my_connection = mysql_connect('localhost','root','');
if(!$my_connection){
die('Could not connect: ' . mysql_error());
}
echo 'Connected successfully' . '<br><br>';
$my_database = mysql_select_db('jihoon');
if(!$my_database){
die('Could not find database: ' . mysql_error());
}
$query='SELECT * FROM comments";
$result=mysql_query($query);
$my_rows;
while($row = mysql_fetch_array($result, MYSQL_ASSOC)){
$my_rows = $my_rows . "id : {$row['id']}";
}
mysql_close($my_connection);
?>