Question

I have an array of letters that are used to create a header and sort an array of listItems from my database. What i have right now is:

$alph = array('a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't', 'u', 'v', 'w', 'x', 'y', 'z');                        
foreach($alph as $data) {
   echo  "<h3 id=" . $data .">" . $data . "</h3><br />";
   foreach($list as $listItem) {
    if(strtolower(substr($listItem->title, 0, 1)) === $data) {
        echo $listItem;
        }
   }
}

This works great but I feel there may be improvements that can be made to increase speed.

Answer 1

Solution that is O(n) i think, but cheats with php hash arrays:

// create empty index
$index = array_fill_keys(range('a', 'z'), array());
// index items by first letter
foreach ($list as $it) {
  $index[strtolower(substr($it->title, 0, 1))][] = $it;
}
// print all
foreach ($index as $letter => $items) {
  echo "<h3 id='$letter'>$letter</h3>";
  foreach ($items as $it) {
    echo $it;
  }
}