初始化数组以使用外部循环的mysql输出

Why the print_r don't output any data?

 $host = array();
 while($row = mysqli_fetch_array($result))
  {
  $host = parse_url($row['url'], PHP_URL_HOST); 
  //echo $host;
  echo "<br>";
  }

print_r($host);

What is the correct way to do this. Thanks in advance.

Change this:

$host = parse_url($row['url'], PHP_URL_HOST);

For this:

$host[] = parse_url($row['url'], PHP_URL_HOST);

http://php.net/manual/en/language.types.array.php