PHP Auto-correcting URLs - php

Question

I dont wan't reinvent wheel, but i couldnt find any library that would do this perfectly.
In my script users can save URLs, i want when they give me list like:
google.com
www.msn.com
http://bing.com/
and so on...
I want to be able to save in database in "correct format".
Thing i do is I check is it there protocol, and if it's not present i add it and then validate URL against RegExp.
For PHP parse_url any URL that contains protocol is valid, so it didnt help a lot.
How guys you are doing this, do you have some idea you would like to share with me?
Edit:
I want to filter out invalid URLs from user input (list of URLs). And more important, to try auto correct URLs that are invalid (ex. doesn't contains protocol). Ones user enter list, it should be validated immediately (no time to open URLs to check those they really exist).
It would be great to extract parts from URL, like parse_url do, but problem with parse_url is, it doesn't work well with invalid URLs. I tried to parse URL with it, and for parts that are missing (and are required) to add default ones (ex. no protocol, add http). But parse_url for "google.com" wont return "google.com" as hostname but as path.
This looks like really common problem to me, but i could not find available solution on internet (found some libraries that will standardize URL, but they wont fix URL if it is invalid).
Is there some "smart" solution to this, or I should stick with my current:
Find first occurrence of :// and validate if it's text before is valid protocol, and add protocol if missing
Found next occurrence of / and validate is hostname is in valid format
For good measure validate once more via RegExp whole URL
I just have feeling I will reject some valid URLs with this, and for me is better to have false positive, that false negative.

Answer 1

I had the same problem with parse_url as OP, this is my quick and dirty solution to auto-correct urls(keep in mind that the code in no way are perfect or cover all cases):
Results:
http:/wwww.example.com/lorum.html => http://www.example.com/lorum.html
gopher:/ww.example.com => gopher://www.example.com
http:/www3.example.com/?q=asd&f=#asd =>http://www3.example.com/?q=asd&f=#asd
asd://.example.com/folder/folder/ =>http://example.com/folder/folder/
.example.com/ => http://example.com/
example.com =>http://example.com
subdomain.example.com => http://subdomain.example.com
function url_parser($url) {
// multiple /// messes up parse_url, replace 2+ with 2
$url = preg_replace('/(\/{2,})/','//',$url);
$parse_url = parse_url($url);
if(empty($parse_url["scheme"])) {
$parse_url["scheme"] = "http";
}
if(empty($parse_url["host"]) && !empty($parse_url["path"])) {
// Strip slash from the beginning of path
$parse_url["host"] = ltrim($parse_url["path"], '\/');
$parse_url["path"] = "";
}
$return_url = "";
// Check if scheme is correct
if(!in_array($parse_url["scheme"], array("http", "https", "gopher"))) {
$return_url .= 'http'.'://';
} else {
$return_url .= $parse_url["scheme"].'://';
}
// Check if the right amount of "www" is set.
$explode_host = explode(".", $parse_url["host"]);
// Remove empty entries
$explode_host = array_filter($explode_host);
// And reassign indexes
$explode_host = array_values($explode_host);
// Contains subdomain
if(count($explode_host) > 2) {
// Check if subdomain only contains the letter w(then not any other subdomain).
if(substr_count($explode_host[0], 'w') == strlen($explode_host[0])) {
// Replace with "www" to avoid "ww" or "wwww", etc.
$explode_host[0] = "www";
}
}
$return_url .= implode(".",$explode_host);
if(!empty($parse_url["port"])) {
$return_url .= ":".$parse_url["port"];
}
if(!empty($parse_url["path"])) {
$return_url .= $parse_url["path"];
}
if(!empty($parse_url["query"])) {
$return_url .= '?'.$parse_url["query"];
}
if(!empty($parse_url["fragment"])) {
$return_url .= '#'.$parse_url["fragment"];
}
return $return_url;
}
echo url_parser('http:/wwww.example.com/lorum.html'); // http://www.example.com/lorum.html
echo url_parser('gopher:/ww.example.com'); // gopher://www.example.com
echo url_parser('http:/www3.example.com/?q=asd&f=#asd'); // http://www3.example.com/?q=asd&f=#asd
echo url_parser('asd://.example.com/folder/folder/'); // http://example.com/folder/folder/
echo url_parser('.example.com/'); // http://example.com/
echo url_parser('example.com'); // http://example.com
echo url_parser('subdomain.example.com'); // http://subdomain.example.com

Answer 2

It's not 100% foolproof, but a 1 liner.
$URL = (((strpos($URL,'https://') === false) && (strpos($URL,'http://') === false))?'http://':'' ).$URL;
EDIT
There was apparently a problem with my initial version if the hostname contain http.
Thanks Trent