PHP | FilesystemIterator next() Function

<?php

// Create new file system iterator
$fileItr = new FilesystemIterator(dirname(__FILE__));

// Check for validity of file iterator
while ($fileItr->valid()) {

    // Check for directory
    if ($fileItr->isDir()) {

        // Display the filename
        echo $fileItr->getFilename() . "<br>";
    }

    // Move to the next element
    $fileItr->next();
}

?>

<?php

// Create new file system iterator
$fileItr = new FilesystemIterator(dirname(__FILE__), 
        FilesystemIterator::KEY_AS_FILENAME);

// Loop runs while file iterator is valid
while ($fileItr->valid()) {

    // Check if file iterator is not directory
    if (!$fileItr->isDir()) {

        // Display the key element
        echo $fileItr->key() . "<br>"; 
    }

    // Move to the next element
    $fileItr->next();
}

?>