Error Warning: join(): Invalid arguments passed in PHP [duplicate] - php

Question

This question already has answers here:
ErrorException : implode(): Passing glue string after array is deprecated. Swap the parameters
(6 answers)
Closed 4 months ago.
Please help,
i got error "Warning: join(): Invalid arguments passed in ... on line...".
Here is my code:
$query = "SELECT `id`, `kategori`, `sub_kategori` FROM `table` ORDER BY `id` DESC";
$stmt = $DB_con->prepare($query);
$stmt->execute();
$kategori = array();
if($stmt->rowCount()>0) {
while($row=$stmt->fetch(PDO::FETCH_ASSOC)){
$kategori = print($row['kategori']);
}
}else{
echo "Nothing here...";
}
join($kategori, ',');
I expect the output : Data,Data,Data,Data,Book,Book
but the actual output is "DataDataDataDataBookBook" anda error "Warning: join(): Invalid arguments passed in ... on line..."

Answer 1

Just append $row['kategori'] in each iteration and change the order of parameteres in join() or implode() call:
<?php
// Get data
$query = "SELECT `id`, `kategori`, `sub_kategori` FROM `table` ORDER BY `id` DESC";
$stmt = $DB_con->prepare($query);
$stmt->execute();
// Fetch data
$kategori = array();
if ($stmt->rowCount() > 0) {
while($row = $stmt->fetch(PDO::FETCH_ASSOC)) {
$kategori[] = $row['kategori'];
}
} else {
echo "Nothing here...";
}
// Output
echo implode(',', $kategori);
?>

Answer 2

An alternative to fetching a bunch of records and then joining them together would be to use GROUP_CONCAT() in mysql to do the work for you. Also as you are not binding anything - you can just call query(). Then you will have 1 row from the database with the content - so the last bit is to say if it's empty, then set the value to Nothing here... (done using ?:)
...
$query = "SELECT GROUP_CONCAT(`kategori`) as kategori
FROM `table`
ORDER BY `id` DESC";
$stmt = $DB_con->query($query);
$row=$stmt->fetch(PDO::FETCH_ASSOC);
$output = $row['kategori']?:"Nothing here...";
echo $output;
If you still need the individual data rows, then another alternative is to use PDO::FETCH_COLUMN and fetchAll() to return the results, then implode() as in the other solution...
$query = "SELECT `kategori`
FROM `table`
ORDER BY `id` DESC";
$stmt = $DB_con->query($query);
$kategori=$stmt->fetchAll(PDO::FETCH_COLUMN);
echo implode(',', $kategori)?:"Nothing here...";