PHP & MySQL check database if data is entered question.

Question

I was wondering how can I check if there is no tags entered into the database for a specific post if there are none, display no tags have been entered. How can I do this using PHP?

Here is my PHP & MySQL code.

$tag = array();
$dbc = mysqli_query($mysqli, "SELECT tags.tag
                  FROM posts_tags 
                  INNER JOIN tags ON tags.id = posts_tags.tag_id 
                  WHERE posts_tags.post_id = '" . $post_id . "' 
                  GROUP BY tags.tag");

if (!$dbc) {
    print mysqli_error($mysqli);
}  else {
    while($row = mysqli_fetch_array($dbc)){
    $tag[] = $row['tag'];
    }
}

Answer 1

If the tag array is empty, then there are no tags:

if(empty($tag)){
   echo 'no tags have been entered';
}

You could also check for the number of rows returned:

if(mysqli_num_rows($dbc) == 0){
   echo 'no tags have been entered.';
}

Answer 2

Use mysqli_num_rows and code like this:

$tag = array();
$dbc = mysqli_query($mysqli, "SELECT tags.tag
                  FROM posts_tags 
                  INNER JOIN tags ON tags.id = posts_tags.tag_id 
                  WHERE posts_tags.post_id = '" . $post_id . "' 
                  GROUP BY tags.tag");

if (!$dbc)
{
    print mysqli_error($mysqli);
}
elseif(!mysqli_num_rows($dbc))
{
    echo "no tags have been entered";
}
else
{
    while($row = mysqli_fetch_array($dbc))
    {
        $tag[] = $row['tag'];
    }
    print_r($tag);
}