$find = 'oo';
$directory = 'd:\test';
    $search = new RecursiveIteratorIterator(
            new RecursiveDirectoryIterator($directory, FilesystemIterator::SKIP_DOTS),
            RecursiveIteratorIterator::SELF_FIRST
        );


    $search = new RegexIterator($search, '/'.$find.'/i');

d:testbar foo;
d:testfoo bar;
d:testtext.txt;
d:testfoo.txt;

d:testfoo bar;
d:testbar foo;
d:testfoo.txt;