» Domainnamen / Hostnamen validieren

function is_valid_domain_name($domain_name)
{
    return (preg_match("/^([a-z\d](-*[a-z\d])*)(\.([a-z\d](-*[a-z\d])*))*$/i", $domain_name) //valid chars check
            && preg_match("/^.{1,253}$/", $domain_name) //overall length check
            && preg_match("/^[^\.]{1,63}(\.[^\.]{1,63})*$/", $domain_name)   ); //length of each label
}

function filter_hostname($name, $domain_only=false) {
	// entire hostname has a maximum of 253 ASCII characters
	if (!($len = strlen($name)) || $len > 253
	// .example.org and localhost- are not allowed
	|| $name[0] == '.' || $name[0] == '-' || $name[ $len - 1 ] == '.' || $name[ $len - 1 ] == '-'
	// a.de is the shortest possible domain name and needs one dot
	|| ($domain_only && ($len < 4 || strpos($name, '.') === false))
	// several combinations are not allowed
	|| strpos($name, '..') !== false
	|| strpos($name, '.-') !== false
	|| strpos($name, '-.') !== false
	// only letters, numbers, dot and hypen are allowed
	|| preg_match('/[^a-z\d.-]/i', $name)
	) {
		return false;
	}
	// each label may contain up to 63 characters
	$offset = 0;
	while (($pos = strpos($name, '.', $offset)) !== false) {
		if ($pos - $offset > 63) {
			return false;
		}
		$offset = $pos + 1;
	}
	return $name;
}

<?php
function filter_hostname($name, $domain_only=false) {
	// entire hostname has a maximum of 253 ASCII characters
	if (!($len = strlen($name)) || $len > 253
	// .example.org and localhost- are not allowed
	|| $name[0] == '.' || $name[0] == '-' || $name[ $len - 1 ] == '.' || $name[ $len - 1 ] == '-'
	// a.de is the shortest possible domain name and needs one dot
	|| ($domain_only && ($len < 4 || strpos($name, '.') === false))
	// several combinations are not allowed
	|| strpos($name, '..') !== false
	|| strpos($name, '.-') !== false
	|| strpos($name, '-.') !== false
	// only letters, numbers, dot and hypen are allowed
/*
	// really slow
	for ($i = 0; $i < $len; $i++) {
		if (stripos('abcdefghijklmnopqrstuvwxyz0123456789.-', $name[$i]) === false) {
			return false;
		}
	}
	// really slow
	while ($len--) {
		if (stripos('abcdefghijklmnopqrstuvwxyz0123456789.-', $name[$len]) === false) {
			return false;
		}
	}
	// slow
	|| str_ireplace(str_split('abcdefghijklmnopqrstuvwxyz0123456789.-'), '', $name)
	// fast
	|| !ctype_alnum(str_replace(array('-', '.'), '', $name))
*/
	|| preg_match('/[^a-z\d.-]/i', $name)
	) {
		return false;
	}
	// each label may contain up to 63 characters
/*
	// really slow
	if (max(array_map('strlen', explode('.', $name))) > 63) {
		return false;
	}
	// slow
	$labels = explode('.', $name);
	foreach ($labels as $label) {
		if (strlen($label) > 63) {
			return false;
		}
	}
	// fast
	if (!preg_match('/^[^\.]{1,63}(\.[^\.]{1,63})*$/', $name)) {
		return false;
	}
*/
	$offset = 0;
	while (($pos = strpos($name, '.', $offset)) !== false) {
		if ($pos - $offset > 63) {
			return false;
		}
		$offset = $pos + 1;
	}
	return $name;
}
function is_valid_domain_name($domain_name)
{
    return (preg_match("/^([a-z\d](-*[a-z\d])*)(\.([a-z\d](-*[a-z\d])*))*$/i", $domain_name) //valid chars check
            && preg_match("/^.{1,253}$/", $domain_name) //overall length check
            && preg_match("/^[^\.]{1,63}(\.[^\.]{1,63})*$/", $domain_name)   ); //length of each label
}
function is_valid_domain_name2($domain_name) {
	return (
		(($len = strlen($domain_name)) < 254 && $len) //overall length check
		&& preg_match("/^[^\.]{1,63}(\.[^\.]{1,63})*$/", $domain_name) //length of each label
		&& preg_match("/^([a-z\d](-*[a-z\d])*)(\.([a-z\d](-*[a-z\d])*))*$/i", $domain_name) //valid chars check
	);
}
function is_valid_domain_name3($domain_name) {
	return (
		preg_match("/^([a-z\d](-*[a-z\d])*)(\.([a-z\d](-*[a-z\d])*))*$/i", $domain_name) //valid chars check
		&& preg_match("/^[^\.]{1,63}(\.[^\.]{1,63})*$/", $domain_name) //length of each label
		&& (($len = strlen($domain_name)) < 254 && $len) //overall length check
	);
}
$domains = explode(',', 'example.com,sub.EXAMPLE.co.uk,xn--fsqu00a.xn--0zwm56d,xn--4gbrim.xn----ymcbaaajlc6dj7bxne2c.xn--wgbh1c,' . str_repeat('example', 9) . '.' . str_repeat('example', 9) . '.com,a,0,a.b,localhost,exa mple.com,example..com,example.com ,example-.com,.example.com,' . str_repeat('example', 9) . '.' . str_repeat('example', 10) . '.com,' . str_repeat('example', 9) . '.' . str_repeat('example', 9) . '.' . str_repeat('example', 9) . '.' . str_repeat('example', 9) . '.com,e--e.-om,e--e-.om,,<script,alert(,.,.., ,-,');
$real_world = explode(',', 'example.com,sub.EXAMPLE.co.uk,xn--fsqu00a.xn--0zwm56d,xn--4gbrim.xn----ymcbaaajlc6dj7bxne2c.xn--wgbh1c,a,0,a.b,localhost,exa mple.com,example..com,example.com ,example-.com,.example.com,e--e.-om,e--e-.om,,<script,alert(,.,.., ,-,');
// benchmark
$start_time = microtime(true);
for ($i = 0; $i < 10000; $i++) {
	foreach ($real_world as $domain) {
		if (!$i) {
			echo filter_hostname($domain) . PHP_EOL;
		}
		filter_hostname($domain);
	}
}
$end_time = microtime(true);
echo $end_time - $start_time;
filter_hostname($domain);// $domains: 0.43556308746338 $real_world: 0.33749794960022
is_valid_domain_name($domain);// $domains: 0.81832790374756 $real_world: 0.32248711585999
is_valid_domain_name2($domain);// $domains: 0.49456095695496 $real_world: 0.34724116325378
is_valid_domain_name3($domain);// $domains: 0.74682402610779 $real_world: 0.2913498878479
?>

filter_var('127.0.0.1', FILTER_VALIDATE_IP);

<?php
function build_root_url($url) {
	// add scheme http://en.wikipedia.org/wiki/URI_scheme#Generic_syntax
	if (!preg_match('~^[0-9a-z.\-+]{2,}://~i', $url)) {
		$url = 'http://' . $url;
	}
	$scheme_pos = strpos($url, '://');
	// this will fail if "http://example.com"
	$first_slash_pos = strpos($url, '/', $scheme_pos + 3);
	if ($first_slash_pos) {
		// "http://example.com/foo/bar" becomes "http://example.com"
		$url = substr($url, 0, $first_slash_pos);
	}
	// is the hostname valid?
	if (!filter_hostname(substr($url, strpos($url, '://') + 3), true)) {
		return false;
	}
	// "http://example.com" becomes "http://example.com/"
	$url .= '/';
	return $url;
}
$domains = explode(',', 'example,http://.example.com,example.com,http://example.com,http://example.com/,http://example.com/foo/bar,http://foo.example.com,foo.example.com');
foreach ($domains as $domain) {
	echo $domain . ' --> ' . build_root_url($domain) . PHP_EOL;
}
?>

Zitat

example -->
http://.example.com -->
example.com --> http://example.com/
http://example.com --> http://example.com/
http://example.com/ --> http://example.com/
http://example.com/foo/bar --> http://example.com/
http://foo.example.com --> http://foo.example.com/
foo.example.com --> http://foo.example.com/

Mach mit!