PHP Regex not working as expected

I have the path of a file and I want to extract parts of it with a regex. But the pattern seems to be wrong, it only gives me the last match.

$s = 'engine/plugins/renderer_smarty/plugins/css_minify/';
preg_match('@^engine/(plugins/(.+?)/)+$@i',$s,$matches);

Result:

array (3):
    0 => string (50): "engine/plugins/renderer_smarty/plugins/css_minify/"
    1 => string (19): "plugins/css_minify/"
    2 => string (10): "css_minify"

Expected result:

array (5):
    0 => string (50): "engine/plugins/renderer_smarty/plugins/css_minify/"
    1 => string (24): "plugins/renderer_smarty/"
    2 => string (15): "renderer_smarty"
    3 => string (19): "plugins/css_minify/"
    4 => string (10): "css_minify"

What's wrong in the pattern?

Thanks!