127.0.0.3 familiya-in

00:25:00:0F:00:1A 127.0.0.3

192.168.10.2 00:25:00:0F:00:1A

familiya-in 00:25:00:0F:00:1A 192.168.10.2

function readData($name) {
  $res = [];
  $handle = fopen($name, "r");
  if ($handle) {
    while (($str = fgets($handle) !== false) {
      $parsed = explode(' ', $str);
      $res[$parsed[1]] = $parsed[0];
    }
    fclose($handle);
  }
  return res;
}

$mac_list = readData('file2');
$ip_list = readData('file3');
$data = [];
$handle = fopen('file1', "r");
if ($handle) {
  while (($str = fgets($handle) !== false) {
    $parsed = explode(' ', $str);
    $name = $parsed[1];
    $mac = $mac_list[$name];
    $ip = $ip_list[$mac];
    printf('%s %s %s', $name, $mac, $ip);
  }
  fclose($handle);
}

function getAndExplode($fileName, $key = 0) {
    $contents = file_get_contents($fileName);
    $exploded = explode(" ", $contents);
    return $exploded[$key];
}

$string = getAndExplode("file1.txt", 1)
  . " " . getAndExplode("file2.txt")
  . " " . getAndExplode("file3.txt");

echo $string;

// familiya-in 00:25:00:0F:00:1A 192.168.10.2