Php coming with the DirectoryIterator which can be very useful in that case.
Please note that this simple function can be easly improved by adding the whole path to a file instead the only file name, and maybe use something else instead of the reference.
/*
* Find all file of the given type.
* @dir : A directory from which to start the search
* @ext : The extension. XXX : Dont call it with "." separator
* @store : A REFERENCE to an array on which store the element found.
* */
function allFileOfType($dir, $ext, &$store) {
foreach(new DirectoryIterator($dir) as $subItem) {
if ($subItem->isFile() && $subItem->getExtension() == $ext)
array_push($store, $subItem->getFileName());
elseif(!$subItem->isDot() && $subItem->isDir())
allFileOfType($subItem->getPathName(), $ext, $store);
}
}
$jpgStore = array();
allFileOfType(__DIR__, "jpg", $jpgStore);
print_r($jpgStore);