php提取url中的域名

<?php
function extractDomain($url) {
    $pattern = '/^(?:https?:\/\/)?(?:[^@\n]+@)?(?:www\.)?([^:\/\n]+)/';
    preg_match($pattern, $url, $matches);
    return $matches[1] ?? '';
}

$url = 'https://www.example.com/path/to/resource?query=string';
$domain = extractDomain($url);
echo $domain; // 输出: www.example.com
?>

<?php
function extractDomain($url) {
    $parsedUrl = parse_url($url);
    if (isset($parsedUrl['host'])) {
        return $parsedUrl['host'];
    }
    return '';
}

$url = 'https://www.example.com/path/to/resource?query=string';
$domain = extractDomain($url);
echo $domain; // 输出: www.example.com
?>

<?php
function extractRootDomain($domain) {
    $pattern = '/(?:(?:[^.]+\.)?([^.]+\.[^.]+))$/';
    preg_match($pattern, $domain, $matches);
    return $matches[1] ?? '';
}

$domain = 'subdomain.example.com';
$rootDomain = extractRootDomain($domain);
echo $rootDomain; // 输出: example.com
?>

<?php
function isValidUrl($url) {
    return filter_var($url, FILTER_VALIDATE_URL);
}

$url = 'invalid-url';
if (isValidUrl($url)) {
    $domain = extractDomain($url);
    echo $domain;
} else {
    echo 'Invalid URL';
}
?>