gethostbyname - PHP code example

The php Function Gethostbyname()

PHP is a widely used server-side programming language for creating dynamic websites. One of the functions available in PHP to convert a hostname to an IP address is gethostbyname(). In this article, we will look at the function and see how it works.

The php function gethostbyname() returns the IPv4 address for a given domain or host name on success or a string containing the unmodified hostname on failure. This is only an IPv4 address, if you need an IPv6 address use the getaddrinfo function and associated addrinfo structure.

This function uses the Winsock database to resolve a host name to an IP address. This is a very reliable method of finding an IP address, but it may not return the same result on every machine. It is therefore important to test the results before using them in production.

This function takes a single parameter, which is the hostname to search for an IP address for. The name must be a valid domain or hostname, and it can be a fully qualified domain name (FQDN) or a simple hostname. If the name is not a valid domain or hostname, this function will return an error message. If the Winsock database does not have a record for the name, this function will also return an error message. If the error message indicates that no data of the requested type was found, the Winsock function getsaddrinfo can be called to retrieve a specific error number for the request.

gethostbyname example

return false;
 }

 $parsed_home = parse_url( get_option( 'home' ) );
 $same_host = isset( $parsed_home['host'] ) && strtolower( $parsed_home['host'] ) === strtolower( $parsed_url['host'] );
 $host = trim( $parsed_url['host'], '.' );

 if ( ! $same_host ) {
 if ( preg_match( '#^(([1-9]?\d|1\d\d|25[0-5]|2[0-4]\d)\.){3}([1-9]?\d|1\d\d|25[0-5]|2[0-4]\d)$#', $host ) ) {
 $ip = $host;
 } else {
 $ip = gethostbyname( $host );
 if ( $ip === $host ) { // Error condition for gethostbyname(). return false;
 }
 }
 if ( $ip ) {
 $parts = array_map( 'intval', explode( '.', $ip ) );
 if ( 127 === $parts[0] || 10 === $parts[0] || 0 === $parts[0]
 || ( 172 === $parts[0] && 16 <= $parts[1] && 31 >= $parts[1] )
 || ( 192 === $parts[0] && 168 === $parts[1] )
 ) {
 // If host appears local, reject unless specifically allowed.

                    'type' => 'AAAA',
                    'ipv6' => '::12',
                ],
                [
                    'type' => 'A',
                    'ip' => '1.2.3.4',
                ],
            ],
        ]);

        $this->assertSame('foobar.com', DnsMock::gethostbyname('foobar.com'));
        $this->assertSame('1.2.3.4', DnsMock::gethostbyname('example.com'));
    }

    public function testGethostbynamel()
    {
        DnsMock::withMockedHosts([
            'example.com' => [
                [
                    'type' => 'A',
                    'ip' => '1.2.3.4',
                ],
                [

        $this->SendMSG("Passive mode ".($this->_passive?"on":"off"));
        return TRUE;
    }

    function SetServer($host, $port=21, $reconnect=true) {
        if(!is_long($port)) {
            $this->verbose=true;
            $this->SendMSG("Incorrect port syntax");
            return FALSE;
        } else {
            $ip=@gethostbyname($host);
            $dns=@gethostbyaddr($host);
            if(!$ip) $ip=$host;
            if(!$dns) $dns=$host;
            // Validate the IPAddress PHP4 returns -1 for invalid, PHP5 false             // -1 === "255.255.255.255" which is the broadcast address which is also going to be invalid             $ipaslong = ip2long($ip);
            if ( ($ipaslong == false) || ($ipaslong === -1) ) {
                $this->SendMSG("Wrong host name/address \"".$host."\"");
                return FALSE;
            }
            $this->_host=$ip;

$info['wp-core']['fields']['dotorg_communication'] = array(
                'label' => __( 'Communication with WordPress.org' ),
                'value' => __( 'WordPress.org is reachable' ),
                'debug' => 'true',
            );
        } else {
            $info['wp-core']['fields']['dotorg_communication'] = array(
                'label' => __( 'Communication with WordPress.org' ),
                'value' => sprintf(
                    /* translators: 1: The IP address WordPress.org resolves to. 2: The error returned by the lookup. */
                    __( 'Unable to reach WordPress.org at %1$s: %2$s' ),
                    gethostbyname( 'wordpress.org' ),
                    $wp_dotorg->get_error_message()
                ),
                'debug' => $wp_dotorg->get_error_message(),
            );
        }

        // Remove accordion for Directories and Sizes if in Multisite.         if ( ! $is_multisite ) {
            $loading = __( 'Loading…' );

            $info['wp-paths-sizes']['fields'] = array(

return $this;
 }

 /** * Returns if the given host is reserved * * @param string $host * @return boolean */
 private function _isReserved($host){
 if (!preg_match('/^([0-9]{1,3}\.){3}[0-9]{1,3}$/', $host)) {
 $host = gethostbyname($host);
 }

 $octet = explode('.',$host);
 if ((int)$octet[0] >= 224) {
 return true;
 } else if (array_key_exists($octet[0], $this->_invalidIp)) {
 foreach ((array)$this->_invalidIp[$octet[0]] as $subnetData) {
 // we skip the first loop as we already know that octet matches for ($i = 1; $i < 4; $i++) {
 if (strpos($subnetData, $octet[$i]) !== $i * 4) {
 break;
 }

$value = date('Y-m-d', $value);
                        break;

                    case 'email':
                        $value = strtolower($value);
                        if (!$emailValidator->isValid($value)) {
                            unset($value);
                            $valid = false;
                            break;
                        }
                        $host = trim(substr($value, strpos($value, '@') + 1));
                        if (empty($host) || !gethostbyname($host)) {
                            unset($value);
                            $valid = false;
                        }
                        break;

                    case 'text2':
                        foreach (array_keys($value) as $key) {
                            $value[$key] = trim(strip_tags($value[$key]));
                            if (empty($value[$key])) {
                                unset($value[$key]);
                                $valid = false;
                            }

return $hostname;
                }
            }
        }

        return $ipAddress;
    }

    public static function gethostbyname($hostname)
    {
        if (!self::$hosts) {
            return \gethostbyname($hostname);
        }
        if (isset(self::$hosts[$hostname])) {
            foreach (self::$hosts[$hostname] as $record) {
                if ('A' === $record['type']) {
                    return $record['ip'];
                }
            }
        }

        return $hostname;
    }

#[Package('buyers-experience')] class FileUrlValidator implements FileUrlValidatorInterface
{
    public function isValid(string $source): bool
    {
        $host = parse_url($source, \PHP_URL_HOST);
        if ($host === false || $host === null) {
            return false;
        }

        $ip = gethostbyname($host);

        if (str_contains($ip, '[')) {
            return $this->validateIpv6(trim($ip, '[]'));
        }

        return $this->validateIpv4($ip);
    }

    private function validateIpv4(string $ip): bool
    {
        $ipv4 = filter_var(

$result['label'] = __( 'Could not reach WordPress.org' );

 $result['description'] .= sprintf(
 '%s',
 sprintf(
 '%s %s',
 /* translators: Hidden accessibility text. */
 __( 'Error' ),
 sprintf(
 /* translators: 1: The IP address WordPress.org resolves to. 2: The error returned by the lookup. */
 __( 'Your site is unable to reach WordPress.org at %1$s, and returned the error: %2$s' ),
 gethostbyname( 'api.wordpress.org' ),
 $wp_dotorg->get_error_message()
 )
 )
 );

 $result['actions'] = sprintf(
 '<a href="%s" target="_blank" rel="noopener">%s %s</a>',
 /* translators: Localized Support reference. */
 esc_url( __( 'https://wordpress.org/support/forums/' ) ),
 __( 'Get help resolving this issue.' ),
 /* translators: Hidden accessibility text. */