[boredprogrammer]

"If you're using a bootstrap as your front-end framework, then why the <select> element isn't customized in my <form> just as the standard bootstrap dropdowns !?!"

You're not using a <select> element in your example so I'm not sure how this is a solution? If I went to a doctor complaining of sore fingers, I would not be impressed if his recommended solution was to say "ah, but you have perfectly working toes, just use them instead!"