Turn a array into a variable for send in PHPMailer - php

Question

Im trying to turn a array that haves another array from a SQL select into a unique variable to send it for users by PHPMailer, I tried to place the array on variable of PHPMailer so didnt works, thats why Im trying this way that looks a little bit difficult
public static function getUsersByEmail($email) {
$sql = DB::prepare(
"SELECT username FROM users WHERE email=:email ORDER BY id LIMIT 10"
);
$sql->bindParam('email', $email);
$sql->execute();
$accounts = $sql->fetchAll(PDO::FETCH_ASSOC);
return $accounts; // its array
}
public function recoverUsername($email) {
if (User::emailHasAccounts($email) == true) {
$accounts = [User::getUsersByEmail($email)];
$str = implode(",", $accounts); // imploding array
$mail = new Mail([
'email' => $email,
'subject' => SITENAME,
'template' => 'accountslist',
'variables' => json_encode([
'email' => $email,
'accountList' => $str,
'date' => date('d/m/y h:i')
]),
'time' => time(),
'next_attemp' => time(),
'attemps' => 0,
'status' => 0
]);
// $mail->dbInsert();
return true;
} else {
echo "erro";
return false;
}
}

Answer 1

Solution (for PHP 5.5 <)
$accounts = getAccounts();
$rr = array_column($accounts, 'username');
$array = implode(',', $accounts);
$getaccounts = array_map(function ($accounts) {
return $accounts['username'];
}, $accounts);
$var = implode('<br>', $getaccounts);