PHP function to check that you are main page?

define('LIVE', (!in_array($_SERVER['HTTP_HOST'], array('localhost', 'wp-mechanic'))));
if(!function_exists('is_main')){
function is_main(){
$uri = $_SERVER['REQUEST_URI'];
$arr = explode('/', $uri);
$arr = array_filter($arr, 'strlen');
return ((!LIVE && (count($arr)==1)) || (LIVE && empty($arr)));//empty($uri)
}
}