Fetch Mysql Results into serialized data - php

Question

I have this table:
| id | related_id |
| 1 | 100 |
| 1 | 200 |
| 1 | 300 |
| 2 | 400 |
| 2 | 500 |
| 2 | 600 |
I need to retrieve serialized data as:
a:3:{i:1;s:3:"100";i:2;s:3:"200";i:3;s:3:"300";}
Query
SELECT id, related_id from mytable where id = 1;
I'm trying to get this using 'while'
$result = $link->query($query);
$item = array();
while($f = $result->fetch_assoc()){
$id = $f['id'];
if ($id == $f['id']){
$item[] = $f['related_id'];
}
print serialize($item);
break; // for test
}
SOLUTION that works for me (provided by Erwin - Thanks!)
$item = array();
while($f = $result->fetch_assoc()) {
$id = $f['id'];
if (!array_key_exists($id, $item)) {
$item[$id] = [1 => $f['related_id']];
} else {
$item[$id][] = $f['related_id'];
}
}
foreach ($item as $value) {
print serialize($value) . PHP_EOL;
}

Answer 1

Collect first each related_id and store to id array with your while loop. Then print each using foreach.
$item = array();
while($f = $result->fetch_assoc()) {
$id = $f['id'];
if (!array_key_exists($id, $item)) { // create id array if not exist
$item[$id] = [1 => $f['related_id']]; // To start with index 1
} else {
$item[$id][] = $f['related_id']; // Push each new related_id
}
}
foreach ($item as $value) {
print serialize($value); // Print each serialized
echo '<br>'; // New line
}

Answer 2

What you are trying to do is something like this:
$result = $link->query($query);
$items = array();
while($f = $result->fetch_assoc()){
$id = $f['id'];
if(!isset($items[$id])) {
$items[$id] = array();
}
$items[$id][] = $f['related_id'];
}
foreach($items as $item) {
print serialize($item);
}
For your serialized string, you have to work with an array with related_id in the second layer. The first layer is to save all related_id in an array with the same id.

Answer 3

You have 6 rows, 3 have id 1 and 3 have id 2. You are specifying that you want to use these ids as array keys so you will end up with 2 arrays, each holding 3 values.
If you want each row in its own array you do this:
while($f = $result->fetch_assoc()){
$item[] = array($f['id'] => $f['related_id']);
}