I want the highest and the lowest value of a table, why can't I save that value in PHP?

$category = htmlspecialchars($_GET['category']);

$sql = "(SELECT number 
        FROM german 
        WHERE german.category_german LIKE ".$category." 
        ORDER BY number DESC 
        LIMIT 1) as 'high', 
        (SELECT number 
        FROM german 
        WHERE german.category_german LIKE ".$category." 
        ORDER BY number ASC 
        LIMIT 1) as 'low'";
    if ($result = $conn -> query($sql)) {
      while ($row = $result -> fetch_row()) {
        
          $high_value = $row[high];
          $low_value = $row[low];
          $r_n = rand($low_value,$high_value).PHP_EOL;
          echo $r_n;
          }

      }

What am I missing? I want the highest and the lowest value of a table, why can't I save that value in PHP? I just can't access the values. And I tried out MIN and MAX as well, but they didn't function neither:

$category = htmlspecialchars($_GET['category']);

$sql = "SELECT MIN('number') AS 'low', MAX('number') AS 'high' FROM german WHERE german.category_german LIKE ".$category."";
    if ($result = $conn -> query($sql)) {
      while ($row = $result -> fetch_row()) {
          $high_value = $row[high];
          $low_value = $row[low];
          $r_n = rand($low_value,$high_value).PHP_EOL;
          echo $r_n;
          }

      }

As a result of $r_n I only get 0. The database shouldn't be the problem. Beforehand (where I only used the highest value) everything functioned:

$category = htmlspecialchars($_GET['category']);

$sql = "SELECT number FROM german WHERE german.category_german LIKE ".$category." ORDER BY number DESC LIMIT 1";
if ($result = $conn -> query($sql)) {
  while ($row = $result -> fetch_row()) {
    
      $r_n = $row[0];
      $r_n = rand(1,$r_n).PHP_EOL;
      echo $r_n;
      }

  }