How to Retrieve Root Domain from Subdomains in PHP?

PHP: Extracting Root Domain from Subdomains

Query:

How do I retrieve the root domain name from a given subdomain using PHP?

Solution:

The following PHP function can be used to parse and extract the root domain name from a given URL or subdomain:

<code class="php">function get_domain($url)
{
    $pieces = parse_url($url);
    $domain = isset($pieces['host']) ? $pieces['host'] : '';

    if (preg_match('/(?P<domain>[a-z0-9][a-z0-9\-]{1,63}\.[a-z\.]{2,6})$/i', $domain, $regs)) {
        return $regs['domain'];
    }
    return false;
}</code>

Example:

To retrieve the root domain name from a given subdomain, simply pass the subdomain as an argument to the function:

<code class="php">print get_domain("here.example.com"); // outputs 'example.com'</code>

Additional Considerations:

• The function assumes that all domains have a 3-letter Top-Level Domain (TLD).
• The function handles both URLs and subdomains.

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