(PHP 5)
DirectoryIterator::valid — Check whether current DirectoryIterator position is a valid file
Check whether current DirectoryIterator position is a valid file.
This function has no parameters.
   Returns TRUE if the position is valid, otherwise FALSE
  
Example #1 A DirectoryIterator::valid() example
<?php
$iterator = new DirectoryIterator(dirname(__FILE__));
// Loop to end of iterator
while($iterator->valid()) {
    $iterator->next();
}
$iterator->valid(); // FALSE
$iterator->rewind(); 
$iterator->valid(); // TRUE
?>