Explode a comma in an array value - codeigniter

Question

I want to add comma in array return value.
My code is
$to_ids_string = "";
$to_id = $this->input->post('to');
for ($r = 0; $r < count($this->input->post('to')); $r++) {
if ($to_ids_string != "") {
$to_ids_string = $to_ids_string . "," . $to_id[$r];
} else {
$to_ids_string = $to_id[$r];
}
}
$a = explode(',', $to_ids_string);
foreach ($a as $item) {
$user_id = $item;//echo $user_id;
$email_id['to_email'] = $this->admin_model-
>get_email_id($user_id);
$b = implode(',',$email_id[0]['to_email']);
echo $b;
}exit;
when i print $email_id['to_email'] it will return
Array ( [0] => Array ( [email] => dipti#gmail.com ) ) Array ( [0] => Array ( [email] => abc#gmail.com ) ) but i want to return email with separated by comma.so i use implode function above but it return error as Message: Array to string conversion

Answer 1

Now only i notice that it's inside the foreach . so each time you will get only one mail . so you need to concatenate like this .declare the variable outside the foreach as empty variable like this $b.=''; then inside foreach concatenate like this $b.=$email_id['to_email'][0]['email'].','; after foreach you need to remove the additional comma at end of string using rtrim()
$b='';
foreach ($a as $item) {
$user_id = $item;//echo $user_id;
$email_id['to_email'] = $this->admin_model>get_email_id($user_id);
$b.=$email_id['to_email'][0]['email'].',';
}
echo rtrim($b,',');