Hey thank you so much for sharing code I was trying to build this code from last few days but i can't achieved displaying properly in dropdown upto infinite level.It works & shows subcategoris after respective parent but one can't differentiate it. Your one is perfect.
My function was as follows
<?php
function finddepth($byid)
{
//check weather category has child
//echo "**Passed Id=".$byid;
$re_query=mysql_query("SELECT FROM categories where parent='$byid'");
$num_rows = mysql_num_rows($re_query);
//echo " Has children:".$num_rows."
";
if(mysql_num_rows($re_query) > '0')
{
while($recursive_rw=mysql_fetch_array($re_query))
{
$p=$recursive_rw['id'];
$catnm=$recursive_rw['category'];
$parent=$recursive_rw['parent'];
$pre="|_";
if($parent=="0")
{
?>
<option><?php echo $catnm; ?></option>
<?php
}
else
{
echo '<option>'.$pre.$catnm.'</option>' ;
}
finddepth($p);
}//end while
}//end if
}//end of function
?>