Count instances in table and capture the id of every instance - php

Question

What I'm trying to do is search through my table and count the instances of a letter, and store the ID of each instance in mysql and php (PDO).
What I had been messing around with is this:
$user = 'john';
$stmt = $pdo->prepare("SELECT id, SUBSTR(surname, 1, 1) as surname_init,COUNT(*) as count FROM first_table WHERE user = :user GROUP BY surname_init ORDER BY count DESC");
$stmt->bindValue(":user", $user);
$stmt->execute();
$row = $stmt->fetchAll(PDO::FETCH_ASSOC);
var_dump($row);
This is the result:
array (size=2)
0 =>
array (size=3)
'id' => string '3' (length=1)
'surname_init' => string 'B' (length=1)
'count' => string '2' (length=1)
1 =>
array (size=3)
'id' => string '7' (length=1)
'surname_init' => string 'D' (length=1)
'count' => string '1' (length=1)
So I have two results: B has 2 instances, D has one. However "B" has only one resulting id returned from two.
Is this possible? I think I'm missing something here..

Answer 1

Use GROUP_CONCAT() to get all rows that matched the group by, like:
SELECT
GROUP_CONCAT(id) AS id_list,
SUBSTR(surname, 1, 1) as surname_init,
COUNT(*) as count
FROM first_table
WHERE user = :user
GROUP BY surname_init
ORDER BY count DESC

Answer 2

See if this helps:
$user = 'john';
// use this to get unique starting characters for surnames for the user John
$stmt = $pdo->prepare("SELECT SUBSTR(surname, 1, 1) as `surname_init`,
COUNT(*) as `count` FROM first_table
WHERE user = :user GROUP BY
surname_init ORDER BY count DESC");
$stmt->bindValue(":user", $user);
$stmt->execute();
$rows1 = $stmt->fetchAll(PDO::FETCH_ASSOC);
foreach ($rows1 as $row1){
echo "<BR>Starting Letter: " . $row1['surname_init'];
echo "<BR>Count: " . $row1['count'];
// now get all the IDs for this user that have the
// surnames starting with this alphabet
$stmt = $pdo->prepare("SELECT ID, SUBSTR(surname, 1, 1) as `surname_init`,
FROM first_table
WHERE user = :user
AND surname LIKE :surname");
$stmt->bindValue(":user", $user);
$stmt->bindValue(":surname", $row1['surname_init']."%");
$stmt->execute();
$rows2 = $stmt->fetchAll(PDO::FETCH_ASSOC);
foreach ($rows2 as $row2){
// do insert based on ID here
}
}