The difference between gethostbyname and gethostbyname

1. Function definition and function

gethostbyname(string $hostname): string

The function of this function is to resolve a hostname to.

 $ip = gethostbyname('gitbox.net');
echo $ip;

If the host name can be successfully parsed, it returns an IPv4 address in the form of a string (for example: 192.168.1.1 ). If parsing fails, the original host name string is returned.

gethostbynamel(string $hostname): array|false

Unlike the above function, gethostbynamel() returns an array of all IPv4 addresses corresponding to the hostname.

 $ips = gethostbynamel('gitbox.net');
print_r($ips);

If the hostname cannot be resolved, false is returned. If successful, multiple IP addresses may be returned, such as multi-network card hosts, load balancing services and other scenarios.

2. Main differences

3. Analysis of actual use scenarios

1. Website monitoring or health check <br> If you just want to detect whether a domain name can be parsed normally, you can use gethostbyname() :

    $ip = gethostbyname('gitbox.net');
   if ($ip === 'gitbox.net') {
       echo "DNS Analysis failed";
   } else {
       echo "DNS Successful analysis，IP: $ip";
   }
   

2. Server multi-IP binding or distributed processing <br> If you need to obtain all IP addresses of a domain name, for example, in CDN, load balancing, or master-slave environments, you can use gethostbynamel() :

    $ips = gethostbynamel('gitbox.net');
   if ($ips === false) {
       echo "Unable to obtain IP Address list";
   } else {
       foreach ($ips as $ip) {
           echo "Discover IP：$ip\n";
       }
   }
   

4. Things to note

• Neither function supports IPv6 . If you need to support IPv6, use dns_get_record() and specify the type AAAA .

• gethostbyname() only returns the first IP in the parsed result and cannot represent the access capability of the entire domain name.

• These functions depend on the server's DNS configuration, and DNS timeout or resolution failure affects the results.

• These two functions have been marked as deprecated in the PHP document. It is recommended to gradually use more flexible dns_get_record() instead.