PHP修剪www如果存在并删除路径

Question

I have an array of domain names, like:

array(
'http://example.co.uk/foo/bar',
'http://www.example.com/foo/bar',
'http://example.net/foo/bar')

And so on.

I am using

parse_url($url, PHP_URL_HOST);

to trim everything and just keep the domain name and it's working partly however, it's keeping the www part if it exists. How can I remove the 'www' if it exists. I tried to explicitly remove it from the domain name in the array, but when it resolves it reverts back to www.example.com.

So I'd like to return:

www.example.com/foo/bar > example
www.example.co.uk/foo/bar > example
example.com/foo/bar > example
example.net/foo/bar > example

Answer 1

The function below is not a general purpose function to get the domain name or domain part of a FQDN. Rather it will return the first label (from left to right) if it is not www, and the second label if it is. As requested above.

<?php

function get_domain_from_host($host)
{
    $parts = explode('.', $host);
    $domain = strpos($host, 'www') === 0
        ? next($parts)
        : current($parts);

    return $domain;
}

function test()
{
    $urls_wanted = array(
        'http://www.example.com/foo/bar' => 'example',
        'http://www.example.co.uk/foo/bar' => 'example',
        'http://example.com/foo/bar' => 'example',
        'http://example.net/foo/bar' => 'example'
    );

    foreach($urls_wanted as $url => $wanted) {
        $host   = parse_url($url, PHP_URL_HOST);
        $domain = get_domain_from_host($host);
        print assert($wanted == $domain);
    }
}

test(); // Outputs: 1111

Example use (copy the function above):

$url    = 'http://www.example.com/foo/bar';
$host   = parse_url($url, PHP_URL_HOST);
$domain = get_domain_from_host($host);
echo $domain; // output is 'example'.