Is there a way to retrieve current system *fully qualified domain name* using **php-cli**?

What I'm looking for is php function to retrieve the same thing that hostname -f is doing:

```
$ hostname -f  #returns needed: system01.dev.lan

```

I tried following:

```
php_uname('n') // returns: system01
gethostname() // returns: system01
gethostbyname(gethostname()) // returns ip address
gethostbyname(gethostname() . '.') // returns system01

```

$\_SERVER dose not exist (because only cli env)

Again, I know I can do this

```
php -r "var_dump(shell_exec('hostname -f'));"

```

But for this trivial task, I think php should have built in functionality to retreive fqdn.