PHP:通过URL获取外部网站的主机名(确定主机名中是否包含'www')

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

function hasWWW($hostname) {
    if (strpos($hostname, 'www.') === 0) {
        return true;
    }
    return false;
}

// 测试URL
$url = 'http://www.example.com/page.html';

$hostname = getHostname($url);
if ($hostname !== null) {
    echo "Hostname: " . $hostname . "\n";
    if (hasWWW($hostname)) {
        echo "Contains 'www'\n";
    } else {
        echo "Does not contain 'www'\n";
    }
} else {
    echo "Invalid URL\n";
}
?>

function getHostnameWithRegex($url) {
    preg_match('@^(?:http://)?(?:www\.)?([^:/?#]+)@i', $url, $matches);
    return isset($matches[1]) ? $matches[1] : null;
}