Transform datetime from dd-mm-yyyy to yyyy-mm-dd

gistfile1.txt

#!/bin/php
<?php

$db = new PDO('mysql:host=yourhost;dbname=yourdb;charset=utf8', 'yourusername', 'yourpassword');
$stmt = $db->query("SELECT id, datum FROM yourtable");
$records = [];

while ($obj = $stmt->fetchObject()) {
    $records[$obj->id] = implode('-', array_reverse(explode('-', $obj->datum)));
}

foreach ($records as $id -> $date) {
    $stmt = $db->prepare("UPDATE yourtable SET datum2=:date where id=:id");
    
    $stmt->bindParam(':id', $id, PDO::PARAM_INT);
    $stmt->bindParam(':date', $date, PDO::PARAM_STR);
}