How to write this statement using PHP & CodeIgniter

Question

Hi. I'm trying to figure out how to write a statement in my first CI app (and only second PHP app ever) and I'm stuck.

I have a junction table that holds book_id and user_id from their respective tables. I want to find out who has read a book and echo that back out, but I need the formatting to make sense. Here is the query:

$readQuery = $this->db->get_where('books_users', array('book_id' => $isbn));

And here's my logic for one person

// Get my user info
$user = $this->ion_auth->get_user();
// Tell me who has read it.
$this->db->select('user_id');
$readQuery = $this->db->get_where('books_users', array('book_id' => $isbn));
// If only one person has read it
if ($readQuery->num_rows() == 1) {
    $readResult = $readQuery->row();
    // And if that person was me...
    if ($readResult->user_id == $user->id) {
        $message = 'You have read this.';
    // If it was someone else...
    } else {
        $reader = $this->ion_auth->get_user($readResult->user_id);
        $message = "$reader->first_name $reader->last_name has read this";
    }
// If two people have read it
}

So I'm good if only one person has read it. But when two people have read it, I want it to say "Name One and Name Two have read this." if the logged in person hasn't read it. If they're one of the two people, it should say "You and Name Two have read this".

And so on for 3-5. If 3-5 people have read it, the options would be "Name One, Name Two, and Name Three have read this" or "You, Name Two, and Name Three have read this." up to five people

And if it's 6 or more, it should just say the names of two of them, IE "You, Name Two, and 5 other people have read this."

I considered doing a conditional for each instance and then pushing all of the users to an array. Then I could use in_array() to see if the logged-in user has read it and try to report back, but I'm just having some trouble working up the logic.

Is there an easier way?

Thanks much in advance, Marcus

Answer 1

I'd say use a switch statement with ranges. You'll have to do a bit of acrobatics to handle the issue of including "You" or not. The code below is untested but give you the general idea.

$message = "";
$readers = array();
$me_included = 0; // Counter increment if you're included in the reader list

$this->db->select('user_id');
$readQuery = $this->db->get_where('books_users', array('book_id' => $isbn));      
foreach ($readQuery->result() as $row) {
  if ($row->user_id == $user->id) {
    $message = "You";
    $me_included = 1;
  } else {
    $readers[] = $this->ion_auth->get_user($row->user_id);
  }
}

$reader_count = $sizeof($readers) + $me_included;
switch(TRUE) 
{
  // One reader, not you
  case( ($reader_count == 1) && ($me_included == 0) ):
    $message .= $readers[0]->first_name . " " . $readers[0]->last_name . " has read this.";
    break;
  // Only you
  case( ($reader_count == 1) && ($me_included == 1) ):
    $message .= " have read this.";
    break;
  // Two readers
  case( ($reader_count == 2) ):
    for ($i = 0; $i <= sizeof($readers); $i++) {
      if ($i == sizeof($readers)) {
        $message .= " and ";
      }
      $message .= $readers[i]->first_name . " " . $readers[i]->last_name;
    }
    $message .= " have read this.";
    break;
  case( ($reader_count > 3) && ($reader_count < 6) ):
    if ($me_included) {
      $message .= ", ";
    }
    for ($i = 0; $i <= sizeof($readers); $i++) {
      if ($i == sizeof($readers)) {
        $message .= " and ";
      }
      $message .= $readers[i]->first_name . " " . $readers[i]->last_name;
      if ($i != sizeof($readers)) {
        $message .= ", ";
      } else {
        $message .= " have read this.";
      }
    }
    break;
  case( ($reader_count > 6) ):
    if ($me_included) {
      $message .= ", " . $readers[0]->first_name . " " . $readers[0]->last_name . " and " . ($reader_count - 2) . " others have read this.";
    } else {
    for ($i = 0; $i <= 1; $i++) {
      $message .= $readers[0]->first_name . " " . $readers[0]->last_name . ", " . $readers[1]->first_name . " " . $readers[1]->last_name . " and " . ($reader_count - 2) . " others have read this.";
    }
    break;
  }

Answer 2

$users = array();
while($row)
{
  if(currentuser)
  {
    array_unshift($users,'You')
  }
  else
  {
    $users[] = row[name]
  }
}

$count = $max = count($users);
if($max >= 6)
{
  $max = 2;
}

$str = '';
for($i=0;$i<$max;$i++)
{
  $str .= ($str == '' ? '' : ($i == $count-1 && $count < 6 ? ' And ' : ', ') ) . $users[$i];
}

if($count >= 6)
{
  $str .= ' and '.$count-2.' others'
}

This should help you along. It's pretty much pseudo-code but the logic is there to achieve what you want (I believe). You'd obviously want to not fetch all the rows if you are just showing a number of users but that can easily be accomplished.

Answer 3

There are actually a couple places we can optimize this.

1) In the initial query do a JOIN with the user table so we don't have to query again multiple times just for each name:

$readers = $this->db->select('id', 'first_name', 'last_name')->from('books_users')->join('users', 'books_users.id =users.id', 'left')->where('book_id' => $isbn);

2) Additionally, we can avoid iterating over the entire (potentially large) result set just to see if you read it, by doing a separate query:

$you_read = $this->db->get_where('books_users', array('book_id' => $isbn, 'user_id' => $user->id));

Answer 4

Just for the sake of completeness, here is the final code I used. Hopefully it will be of use to someone.

    // Find out who has read this book
    // Get the users
    $current_user = $this->ion_auth->get_user();
    $users = $this->ion_auth->get_users();
    // Get the readers
    $this->db->select('user_id');
    $query = $this->db->get_where('books_users', array('book_id' => $isbn));
    // If there were results
    $readers = array();
    if ($query->num_rows() > 0) {
        foreach ($users as $user) {
            if ($current_user->id == $user->id) {
                array_unshift($readers, 'You');
            } else {
                $readers[] = $user->first_name . ' ' . $user->last_name;
            }
            $count = $max = count($readers);
            if ($max >= 6) {
                $max = 2;
            }
            $message = '';
            for ($i = 0; $i < $max; $i++) {
                $message .= ($message == '' ? '' : ($i == ($count - 1) && ($count < 6) ? ' and ' : ', ')) . $readers[$i];
            }
            if ($count >= 6) {
                $message .= ' and ' . ($count - 2) . ' others';
            }
            $message .= ($count == 1 && !$current_user->id ? ' has ' : ' have ') . 'read this.';
        }
    } else {
        $message = '<a href="' . base_url() . 'books/' . $bookResult->filename . '">Be the first to read this.</a>';
    }