sort array by length and then alphabetically

You can put both of the conditions into a usort comparison function.

usort($array, function($a, $b) {
    return strlen($a) - strlen($b) ?: strcmp($a, $b);
});

The general strategy for sorting by multiple conditions is to write comparison expressions for each of the conditions that returns the appropriate return type of the comparison function (an integer, positive, negative, or zero depending on the result of the comparison), and evaluate them in order of your desired sort order, e.g. first length, then alphabetical.

If an expression evaluates to zero, then the two items are equal in terms of that comparison, and the next expression should be evaluated. If not, then the value of that expression can be returned as the value of the comparison function.

The other answer here appears to be implying that this comparison function does not return an integer greater than, less than, or equal to zero. It does.

You can create a custom sort method and use the http://www.php.net/manual/en/function.usort.php function to call it.

Example:

$Collection = array(..); // An array of Genre objects

// Either you must make count a public variable, or create
// an accessor function to access it
function CollectionSort($a, $b)
{
    if ($a->count == $b->count)
    {
        return 0;
    }
    return ($a->count < $b->count) ? -1 : 1;
}

usort($Collection, "CollectionSort");

If you'd like to make a more generic collection system you could try something like this

interface Sortable
{
    public function GetSortField();
}

class Genre implements Sortable
{
    private $genre;
    private $count;

    public function GetSortField()
    {
        return $count;
    }
}

class Collection
{
    private $Collection = array();

    public function AddItem($Item)
    {
        $this->Collection[] = $Item;
    }

    public function GetItems()
    {
        return $this->Collection;
    }

    public function Sort()
    {
        usort($this->Collection, 'GenericCollectionSort');
    }
}

function GenericCollectionSort($a, $b)
{
    if ($a->GetSortField() == $b->GetSortField())
    {
        return 0;
    }
    return ($a->GetSortField() < $b->GetSortField()) ? -1 : 1;
}

$Collection = new Collection();
$Collection->AddItem(...); // Add as many Genre objects as you want
$Collection->Sort();
$SortedGenreArray = $Collection->GetItems();

As already has been mentioned, you need to allocate space for pointers, not chars:

char **array;
array = malloc(bufsize * sizeof(char*));

Also you need to allocate space for separate lines, and copy lines to it:

while ((getline(&line, &bufsize, fp)) != -1) {
  printf("%s", line);
  array[i] = malloc(strlen(line) + 1);
  strcpy(array[i], line);
  i++;
} 

A mistake in your code is that all array[i] points to the same string in variable line, which is refilled by getline() every loop cycle.

It may be useful to read manual about getline. It permits allocation of strings by itself, but don't forget to use free().

array[0] = NULL;
while ((getline(&array[i], &bufsize, fp)) != -1) {
  printf("%s", array[i]);
  array[i + 1] = NULL;
  i++;
}