Try to use RecursiveIteratorIterator in combination with RecursiveDirectoryIterator
$path = realpath('/path/you/want/to/search/in');
$objects = new RecursiveIteratorIterator(
new RecursiveDirectoryIterator($path),
RecursiveIteratorIterator::SELF_FIRST);
foreach($objects as $name => $object){
if($object->getFilename() === 'work.txt') {
echo $object->getPathname();
}
}
Additional reading: