How to insert a variable in a query from .ajax post - php

Question

I thought this will be very simple but i think there is a bug when posting a variable from .ajax to a query. Is there any other way I ca get my result?
here is my jquery:
jQuery_1_4_2(document).ready(function()
{
jQuery_1_4_2('.mainfolder').live("click",function()
{
event.preventDefault();
var ID = jQuery_1_4_2(this).attr("id");
var dataString = 'folder_id='+ ID;
if(ID=='')
{
alert("Serious Error Occured");
}
else
{
jQuery_1_4_2.ajax({
type: "POST",
url: "display_folder.php",
data: dataString,
cache: false,
success: function(html){
jQuery_1_4_2(".right_file").prepend(html);
}
});
}
});
});
here is my display_folder.php
<?php
$folder_id = $_POST['folder_id'];
//echo $folder_id;
$qry=mysql_query("SELECT * FROM tbl_folder WHERE folder_id='$folder_id'");
while($row=mysql_fetch_array($qry))
{
echo $row['folder_name'] . "<br>";
}
?>
Can anybody explain why this not work? i tried to echo $folder_id and it is working, but when you put it inside the query it is not working.
Note: This is not a dumb question where i forgot my connection of db. Thanks

Answer 1

I agree with both you and here I am providing (just for clean display) the same with some little formatting.
var dataString = 'folder_id=1';
$.ajax({
url: "folder.php",
type:'post',
async: false,
data:dataString,
success: function(data){
alert(data);
}
});
and php part where I am getting folder_id properly.
<?php
$postid = $_POST['folder_id'];
//echo $postid;
$link = mysql_connect("localhost","root","");
mysql_select_db("test", $link);
$query = mysql_query("select * from post where id='$postid'");
while($row=mysql_fetch_array($query))
{
echo $row['text'] . "<br>"; //a, b etc in each row
}
?>
So it should work.

Answer 2

Try this in your php code
<?php
$folder_id = addslashes($_POST['folder_id']);
//echo $folder_id;
$qry=mysql_query("SELECT * FROM tbl_folder WHERE folder_id='$folder_id'");
while($row=mysql_fetch_array($qry))
{
echo $row['folder_name'] . "<br>";
}
?>