isTor.php

<?php

function isTor()
{
	$host = array
	(
		$_SERVER['REMOTE_ADDR'],
		$_SERVER['SERVER_PORT'],
		$_SERVER['SERVER_ADDR'],
		'ip-port.exitlist.torproject.org',
	);

	foreach ($host as $key => $value)
	{
		if (filter_var($value, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4) !== false)
		{
			$host[$key] = implode('.', array_reverse(explode('.', $value)));
		}
	}

	return gethostbyname(implode('.', $host)) == '127.0.0.2';
}