loop issue

Warning: Cannot use a scalar value as an array...

[WhosAWhata]

i have

while($entry = $d->read()) {
if($entry!= ".") {
if(is_dir($dir.$f)){
$d[] = "<a href=\"".$PHP_SELF."?dir=".$dir."/".$f."/"\">".$f."</a>"; //line 10
}else{
$f[] = "<a href=\"".$dir.$f"\">".$f."</a>";
}
}
}

it returns
Warning: Cannot use a scalar value as an array in /home/user/www/www/files.php on line 10

help

[WhosAWhata]

nevermind, i see now

i had $d = dir($dir) and overwrote it