/**
 * conver string to hastag
 * @param  string  $string       string you want to convert
 * @param  boolean $with_hashtag if false, it won't return the # sign
 * @return string                Eureka! you got your #hashtag!
 */
function stringToHashtag($string, $with_hashtag = true)
{
    $_string = str_replace(' ', '', $string);
    $_out = preg_replace('/[^a-zA-Z]/', '', strtolower($_string));
    return ($with_hashtag) ? "#". $_out : $_out ;
}