I want to read a dir with dir() function and dir to open is like "images/php" then is_file() function doesn't working correctly ... (return false or NULL)

code:

$d = dir("images/php");
while ($file = $d -> read()) {
   if (is_file($file)) { // <- this line always return false
      ...
   }
}

when i use chdir() function to change directory, all working correctly ...

Must I use chdir() func. ???
is this a regular feature ???

jenik