is_array for MySQL Select Statement with PHP - php

Question

I have a basic PHP function that I am working with. Sometimes, it is passed an array of variables, and other times it is just passed one variable. So, currently, I have something like this:
<?
function do_this($user_id_array) {
$user_ids = array();
foreach ($user_id_array as $single_user_id) {
$sql = 'SELECT username FROM users
WHERE id = $single_unit';
while($row = mysql_fetch_assoc($result)) {
array_push($user_ids, $row['id'];
}
}
return $user_ids;
}
?>
My issue is this: If I call the function and send it only one variable (and not an array), it (obviously) gives me the following error: Invalid argument supplied for foreach()
My question is: How can I change this function in the most efficient way with the least amount of code? Do I have to use an if is_array() statement and just create 2 SELECT statements, one for each case (array and non-array)?
Many thanks!

Answer 1

I see several options:
Pass an array even if it's one element long
Test for is_array() and act accordingly
Add another argument which states whether to check for an int or an array.
I'd go with options 1 or 2, as option 3 is error prone.
Also, there might be a better solution to your problem, you shouldn't have a single query for every user, you should instead use the IN keyword in MySQL, something like this:
$users = (is_array($user_id_array)) ? implode(',',$user_id_array) : $user_id_array;
$query = "SELECT `username` FROM `users` WHERE `id` IN({$users})";

Answer 2

wow. that's a lot of queries. What about to delete foreach and do something like
if (is_array($user_id_array)){
$sql = 'SELECT username,id FROM users
WHERE id IN ('.implode(",", $user_id_array).')';
$result = mysql_query($sql);
while($row = mysql_fetch_assoc($result)){
$users[$row['id']] = $row;
}
}

Answer 3

You can write:
$user_id_array = (array)$user_id_array;

Answer 4

if (!is_array($user_id_array))
$user_id_array = array($user_id_array);

Answer 5

function do_this($user_id_array) {
$ids = array_map('intval', (array)$user_id_array);
$sql = 'SELECT username FROM users
WHERE id IN(' . implode(',', $ids) . ')';
$result = mysql_query($sql);
$usernames = array();
while ($row = mysql_fetch_assoc($result)) {
$usernames[] = row['id'];
}
return $usernames;
}
First line makes sure that you have an array ((array)$user_id_array) and that all values are valid integers. Then a single SQL query is executed for all user ids.