Zend_Validate_Hostname allows you to validate a hostname against a set of known specifications. It is possible to check for three different types of hostnames: a DNS Hostname (i.e. domain.com), IP address (i.e. 1.2.3.4), and Local hostnames (i.e. localhost). By default only DNS hostnames are matched.

Basic usage

A basic example of usage is below:

<?php

require_once 'Zend/Validate/Hostname.php';
$validator = new Zend_Validate_Hostname();
if ($validator->isValid($hostname)) {
    // ostname appears to be valid
} else {
    // hostname is invalid; print the reasons
    foreach ($validator->getMessages() as $message) {
        echo "$message\n";
    }
}

?>

This will match the hostname $hostname and on failure populate $validator->getMessages() with useful error messages.

Validating different types of hostnames

You may find you also want to match IP addresses, Local hostnames, or a combination of all allowed types. This can be done by passing a parameter to Zend_Validate_Hostname when you instantiate it. The paramter should be an integer which determines what types of hostnames are allowed. You are encouraged to use the Zend_Validate_Hostname constants to do this.

The Zend_Validate_Hostname constants are: ALLOW_DNS to allow only DNS hostnames, ALLOW_IP to allow IP addresses, ALLOW_LOCAL to allow local network names, and ALLOW_ALL to allow all three types. To just check for IP addresses you can use the example below:

<?php

require_once 'Zend/Validate/Hostname.php';
$validator = new Zend_Validate_Hostname(Zend_Validate_Hostname::ALLOW_IP);
if ($validator->isValid($hostname)) {
    // ostname appears to be valid
} else {
    // hostname is invalid; print the reasons
    foreach ($validator->getMessages() as $message) {
        echo "$message\n";
    }
}

?>

As well as using ALLOW_ALL to accept all hostnames types you can combine these types to allow for combinations. For example, to accept DNS and Local hostnames instantiate your Zend_Validate_Hostname object as so:

<?php

$validator = new Zend_Validate_Hostname(Zend_Validate_Hostname::ALLOW_DNS | Zend_Validate_Hostname::ALLOW_IP);

?>

Validating International Domains Names

Some Country Code Top Level Domains (ccTLDs), such as de (Germany), support international characters in domain names. These are known as International Domain Names (IDN). These domains can be matched by Zend_Validate_Hostname via extended characters that are used in the validation process. At present the list of supported ccTLDs include: at, ch, li, de, fi, hu, no, se. To match an IDN domain it's as simple as just using the standard Hostname validator since IDN matching is enabled by default. If you wish to disable IDN validation this can be done by by either passing a parameter to the Zend_Validate_Hostname constructor or via the $validator->setValidateIdn() method. You can disable IDN validation by passing a second parameter to the Zend_Validate_Hostname constructor in the following way.

<?php

$validator = new Zend_Validate_Hostname(Zend_Validate_Hostname::ALLOW_DNS, false);

?>

Alternatively you can either pass TRUE or FALSE to $validator->setValidateIdn() to enable or disable IDN validation. If you are trying to match an IDN hostname which isn't currently supported it is likely it will fail validation if it has any international characters in it. Where a ccTLD file doesn't exist in Zend/Validate/Hostname specifying the additional characters a normal hostname validation is performed. Please note IDNs are only validated if you allow DNS hostnames to be validated.

Validating Top Level Domains

By default a hostname will be checked against a list of known TLDs. If this functionality is not required it can be disabled in much the same way as disabling IDN support. You can disable TLD validation by passing a third parameter to the Zend_Validate_Hostname constructor. In the example below we are supporting IDN validation via the second parameter.

<?php

$validator = new Zend_Validate_Hostname(Zend_Validate_Hostname::ALLOW_DNS, true, false);

?>

Alternatively you can either pass TRUE or FALSE to $validator->setValidateTld() to enable or disable TLD validation. Please note TLDs are only validated if you allow DNS hostnames to be validated.