API Reverse IP

<?php
error_reporting(0);
class willysan{
  public $ip;
  public $key;
  public $validkey = "memekcyna";
  public $api = "https://domains.tntcode.com/ip/";
  public $worker1 = 0;
  public $worker2 = 0;
  public function revip(){
      $html =
        file_get_contents($this->api.$this->ip);
    $start = stripos($html, '<textarea cols="50" rows="10">');
    $end = stripos($html, '</textarea>', $offset = $start);
    $length = $end - $start;
    $htmlSection = substr($html, $start, $length);
    $result = str_replace('<textarea cols="50" rows="10">',"",$htmlSection);str_replace('</textarea>',"",$htmlSection);
    if($result != NULL){
      $this->worker1 = 1;
      return $result;
    }
  }

  public function apikey(){
    if($this->key != $this->validkey){
      return "Invalid Api Key";
    }else{
      $this->worker2 = 1;
    }
  }
}

class willy extends willysan {
  public function ip($ip){
      $this->ip = $ip;
      willy::revip();
  }
  public function key($key){
    $this->key = $key;
    willy::apikey();
  }
  public function validate(){
    $worker1 = $this->worker1;
    $worker2 = $this->worker2;
    if($worker1 == NULL){
      echo "Wrong Ip Format";die();
    }elseif($worker2 == NULL){
      echo willy::apikey();die();
    }elseif($worker1 != NULL && $worker2 != NULL){
      echo willy::revip();
    }else{
      echo "ngontol";
    }
  }
}

$willy = new willy();
if(isset($_GET["ip"]) && isset($_GET["key"])){
  if(isset($_GET["key"])){if($_GET["key"] == NULL){echo "Please Enter ApiKey";die();}}
  $willy->ip($_GET["ip"]);
  $willy->key($_GET["key"]);
  $willy->validate();
}else{
  if(isset($_GET["ip"])){if($_GET["ip"] == NULL){echo "Please Enter IP Address";die();}else{echo "Require key parameter";die();}}
  echo "Usage: ?ip=ipaddress&key=apikey";
}