Recursive File Search (PHP)

You should create a filter:

class JpegOnlyFilter extends RecursiveFilterIterator
{
    public function __construct($iterator)
    {
        parent::__construct($iterator);
    }

    public function accept()
    {
        return $this->current()->isFile() && preg_match("/\.jpe?g$/ui", $this->getFilename());
    }

    public function __toString()
    {
        return $this->current()->getFilename();
    }
}

$it = new RecursiveDirectoryIterator("L:\folder\folder\folder");
$it = new JpegOnlyFilter($it);
$it = new RecursiveIteratorIterator($it);

foreach ($it as $file)
    ...

Try this, it uses an array of allowed file types and only echos out the file if the file extension exists within the array.

<?php
$it = new RecursiveDirectoryIterator("L:\folder\folder\folder");
$allowed=array("pdf","txt");
foreach(new RecursiveIteratorIterator($it) as $file) {
    if(in_array(substr($file, strrpos($file, '.') + 1),$allowed)) {
        echo $file . "<br/> \n";
    }
}
?>

You may also find that you could pass an array of allowed file types to your RecursiveDirectoryIterator class and only return files that match.

Let PHP do the job:

$directory = new RecursiveDirectoryIterator('path/to/directory/');
$iterator  = new RecursiveIteratorIterator($directory);
$regex     = new RegexIterator($iterator, '/\.jpe?g$/i', RecursiveRegexIterator::GET_MATCH);

echo '<pre>';
print_r($regex);

<?php
$it = new RecursiveDirectoryIterator("L:\folder\folder\folder");
$display = Array ( 'jpeg', 'jpg' );
foreach(new RecursiveIteratorIterator($it) as $file)
{
    if (in_array(strtolower(array_pop(explode('.', $file))), $display))
        echo $file . "<br/> \n";
}
?>