Extracts the host from a given url

host_extractor.php

<?php

/**
* Extracts the host from the given url>
*
* Example: 
* http://codebuster.de/ = codebuster.de 
* http://codebuster.de/test = codebuster.de
*
* @param string $url
* 
* @return string
*/
function extractHostFromUrl($value)
{
    if (empty ($value)) {
        throw new Exception('value is empty');
    }

    $parser = new \webignition\Url\Url($value);
    if ($parser->getHost() === null) {
        $parser->setScheme('http');
        $parser->setHost($value);
    }

    $parser->setPath('');
    if ( ! $parser->hasHost())
        throw new Exception('no host detected');

    $host = (string) $parser->getHost();

    if (strpos($host, '.') === false)
        throw new Exception('no tld detected');

    $host = preg_replace('/^www\./','', $host);  
    $host = strtolower($host);

    return $host;
}