PHP循环检测每个MySQL字母结果的第一个实例

Question

If I query a database with PHP using MySQLi, how can I detect the first instance of each letter of the alphabet?

If I have a table like -

ID | name
1    Allen
2    John
3    Sally
4    William

and I query

SELECT * FROM table ORDER BY name ASC

Can I have something in my loop that says "if this is the first time you've seen the string in name start with the letter A", echo <a id="a"></a> to create an anchor tag? Then it will proceed to do the same for B,C,D,E,F,G, etc.. Then I can create an alphabetical legend.

Here is my query and loop:

$query = "SELECT * FROM table ORDER BY name ASC";
$result = $db->query($query);
$num = $result->num_rows;
for($i=0; $i < $num; $i++){
    $row = $result->fetch_object();
      //IF THIS IS THE FIRST TIME SEEING $row->name START 
      //WITH A DIFFERENT LETTER OF THE ALPHABET ECHO SOMETHING...
    echo $row->name;
 }

Answer 1

Create an associative array that records which letters you've seen.

$letters_seen = array();

while ($row = $result->fetch_object()) {
    $letter = substr($row->name, 0, 1);
    if (!isset($letters_seen[$letter])) {
        // This is the first time seeing this initial letter
        $letters_seen[$letter] = true;
        echo "<a id='$letter'>$letter</a>";
    }
    echo $row->name;
}