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In an effort to enhance database access with PDO, numerous developers encounter challenges, particularly with "WHERE... IN" queries. Let's delve into the intricacies and discover the proper approach for using a list of items within a PDO prepared statement.
Consider a scenario where you need to delete items from a database based on a list of checked items from a form. Each item has a corresponding ID, which would typically be stored in an array. The conventional "WHERE... IN" query would look something like this:
$query = "DELETE FROM `foo` WHERE `id` IN (:idlist)"; $st = $db->prepare($query); $st->execute(array(':idlist' => $idlist));
However, this approach often results in only the first ID being deleted. This is because PDO interprets the comma-separated list as a single value, hence ignoring the subsequent IDs.
To circumvent this issue, one must leverage placeholders and bind parameters. The approach involves replacing the entire comma-separated list with individual placeholders (question marks) and looping through the array to bind each ID to a placeholder. Here's how you would achieve this:
$idlist = array('260','201','221','216','217','169','210','212','213'); $questionmarks = str_repeat("?,", count($idlist)-1) . "?"; $stmt = $dbh->prepare("DELETE FROM `foo` WHERE `id` IN ($questionmarks)"); foreach ($idlist as $id) { $stmt->bindParam(1, $id); }
This revised approach ensures that each ID is treated as a separate parameter, thereby enabling accurate execution of the query.
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