PHP new strings update in DB with unshift? - php

Question

I have a problem to adding more strings in my database.
The idea is: SELECT information, then added array together, after these UPDATE to database.
These are in one code, but UPDATE not working with summed arrays only separately.
With echo I see the array_unshift is working well, the data is good, but not updating.
Need I change something on the server? Maybe version?
(I don't get mysqli_error!)
//CHECKBOX KIOLVASÁSA DB-BŐL!
$sql = ("SELECT id, checkbox FROM osszesito WHERE id = '$id'");
//$result = mysqli_query($conn, $sql);
//if (mysqli_num_rows($result) > 0) {
if ($result = mysqli_query($conn, $sql)) {
while($row = mysqli_fetch_assoc($result)) {
//EREDETI SOR LISTÁZÁSA
$original_array = array( $row["checkbox"] );
$x ="";
echo 'Eredeti sor: ';
foreach ($original_array as $x)
{
echo "$x "."<br><br>";
}
//EREDETI SOR KIEGÉSZÍTÉSE AZ ÚJ ADATTAL
array_unshift($original_array, $chb);
$last ="";
echo "Új sor: "."<br>";
foreach ($original_array as $last)
{
echo $last."<br>";
}
//ÚJ SOR FRISSÍTÉSE A DB-BEN!
//$sqla = "UPDATE osszesito SET checkbox = '$chb' WHERE id = '$id' ";
$sqla = "UPDATE osszesito SET checkbox = '$last' WHERE id = '$id' ";
if (mysqli_query($conn, $sqla)) {
echo "ÚJ SOR ELMENTVE!";
//header("Location: /megrendelesek/index.php");
} else {
echo "Hiba a beírás során: " . mysqli_error($conn);
}
}
///////////////////////////////////////////////
//LEZÁRÁS
} else {
echo "Jelenleg nincs megrendelés az adatbázisban!";
}
mysqli_close($conn);