Compare domains in php

I wrote a small script that provided a URL (For example: code.google.com/ajax/123/1235/214) Would tell you that the actual domain is: code.google.com

When this is compared to code.google.com it return true of course, i want it to return true when it is compared to (anything).google.com So, i want it to return true whenever the actual d开发者_高级运维omain is the same regardless of the subdomain, how to do that?

(This is NOT a homework question, it is for a project I am working on so please provide as much help as possible)

(if you need more information to understand the problem, please write a comment and I will provide more information immediately)

A solution might be to use something like parse_url to extract the host portion of your URL (that's probably the easiest way to get that information).

Then, you can explode that host, using '.' as separator, to get an array that contains the components of the URL (for instance, you'd have array('code', 'google', 'com'))

And, finally, only compare the last two elements of the array you have for each URL.

That way, you'd compare 'google' and 'com' with the informations from the second URL.

I suppose just using a couple of (simpler) string comparisons might work in some cases ; but don't forget cases like 'www.mywebsite.com' and 'subdomain.website.com' -- just an example to show that comparing end of domain names is not enough ^^

It could use some error checking but you can do something like this:

<?php

function url_belongs_to_domain($url, $domain){
    $url_domain = parse_url($url, PHP_URL_HOST);

    return preg_match('/' . preg_quote($domain, '/') . '$/i', $url_domain)==1;
}

var_dump( url_belongs_to_domain('http://code.google.com/ajax/123/1235/214', 'google.com') );
var_dump( url_belongs_to_domain('http://code.google.com/ajax/123/1235/214', 'code.google.com') );
var_dump( url_belongs_to_domain('http://code.google.com/ajax/123/1235/214', 'www.google.com') );
var_dump( url_belongs_to_domain('http://www.google.com/ajax/123/1235/214', 'google.com') );
var_dump( url_belongs_to_domain('http://www.google.com/ajax/123/1235/214', 'code.google.com') );
var_dump( url_belongs_to_domain('http://www.google.com/ajax/123/1235/214', 'www.google.com') );

?>

bool(true)
bool(true)
bool(false)
bool(true)
bool(false)
bool(true)

Be aware that accurate detection of top level domains requires checking against a list since it doesn't follow any rule: in www.google.com it is google.com, in www.google.co.uk it is google.co.uk.