How do I remove http, https and slash from user input in php

Question

Example user input

http://domain.com/
http://domain.com/topic/
http://domain.com/topic/cars/
http://www.domain.com/topic/questions/

I want

Answer 1

Found this http://refactormycode.com/codes/598-remove-http-from-url-string

function remove_http($url = '')
{
    if ($url == 'http://' OR $url == 'https://')
    {
        return $url;
    }
    $matches = substr($url, 0, 7);
    if ($matches=='http://') 
    {
        $url = substr($url, 7);     
    }
    else
    {
        $matches = substr($url, 0, 8);
        if ($matches=='https://') 
        $url = substr($url, 8);
    }
    return $url;
}