db_insert throws a PDOException when creating a row with implode(). Why?

Question

Drupal

In general, the fact is that when you try to add a row to the database, when forming it through implode (), a PDOException error pops up:
This does not work:

<?php
$test_array = array('Apple', 'Banan');
$test = implode($test_array, ", ");

db_insert('test')
  ->fields(array(
    'nid' => 2,
    'related' => $test,
    'created' => time(),
  ))
  ->execute();

And that's how it works

<?php

$test = 'Apple, Banan';

db_insert('test')
  ->fields(array(
    'nid' => 2,
    'related' => $test,
    'created' => time(),
  ))
  ->execute();

Answer 1

In general, the problem was in the encoding, I did not understand why, but
I solved the problem

Answer 2

The arguments were mixed up in places, at least they looked at the logs, it’s probably written there.