$parts = explode('.',$file->getBasename());
$extension = strtolower(end($parts));

<?php 
error_reporting(E_ALL | E_STRICT);
 
$path = '/path/to/file';
 
$iterator = new RecursiveDirectoryIterator($path);
$recurse = new RecursiveIteratorIterator($iterator, RecursiveIteratorIterator::SELF_FIRST);
echo "<ul>\n";
$x=0;
foreach ( $recurse as $file)
{
	$parts = explode('.',$file->getBasename());
	$extension = strtolower(end($parts));
 
	if( $file->isDir() && !$recurse->isDot() )
	{
		echo "<li><b>{$file->getBasename()}</b></li>\n";
 
	}
	else if( $file->isFile() && $extension == 'zip' )
	{
		//unlink($file->getPathname());
	}
	else if( $file->isFile() && ($extension == 'mp3' || $extension == 'mpa') )
	{
		echo "<li>
		      <input type = \"checkbox\" name = \"file$x\" value = \"{$file->getBasename()}\" />
		      <input type = \"hidden\" name = \"file".$x."_path\" value = \"{$file->getPathname()}\" />
		      <a href=\"{$file->getPathname()}\">{$file->getBasename()}</a>
		      </li>\n";
	}
	++$x;
}
echo "</ul>";

$op = "<select name='opts' id='opts'>";
$dir = new DirectoryIterator( '/www/test/' );
foreach($dir as $file ){
  if(!$file->isDot() && !$file->isDir() && preg_match("/.mp3$/",$file->getFilename())) {
    $op .= "<option value='{$file->getFilename()}'>{$file->getFilename()}</option>";
  }
}
$op .= "<select>";
echo $op;