Question

First of all, I’m using PDO. I believe it can be done using prepare query, but I have no idea how.

The problem is, I got an array with values, and I need to check, if those values exist in the database.

Right now, it looks like:

foreach( $arr as $id ) {
$match =$PDO->query("SELECT `id` FROM `users` WHERE `id` = " . intval($id))->fetch();

if(isset($match['id']))
//exist
else
//not exist.
}

I don’t wan’t to run this query in every loop to check if the $id exist in the database.
So is there any way, to collect all of those values from foreach, and then run a one query to check if each value exist in the database?

Answer 1

How about this:

// Do query
$result = $PDO->query("SELECT `id` FROM `users` WHERE `id` IN (".implode(', ',$arr).")");

// Loop results (i.e. existing)
while ($row = $result->fetch()) {
  // Do exist action here for $row['id']
  unset($arr[array_search($row['id'],$arr)]);
}

// Loop remaining values in $arr (i.e. not existing)
foreach ($arr as $notexist) {
  // Do not exist action here
}