How to Resolve the PHP PDOException 'Invalid Parameter Number' Error in Prepared Statements?

PHP PDOException: Addressing "Invalid Parameter Number" Error

This error typically occurs when a query attempts to bind an incorrect number of parameters to a PDO prepared statement. In the provided code, the error is likely due to the usage of named placeholders in the query string.

The original query:

$sql = "INSERT INTO persist (user_id, hash, expire) VALUES (:user_id, :hash, :expire) ON DUPLICATE KEY UPDATE hash=:hash";

uses the same named placeholder ":hash" for both the initial insert and the update. However, PDO requires unique parameter markers for each value being bound.

To resolve this issue, rename the placeholder in the update clause:

$sql = "INSERT INTO persist (user_id, hash, expire) VALUES (:user_id, :hash, :expire) ON DUPLICATE KEY UPDATE hash=:hash2";

Additionally, the bind an array of parameters to the execute() method:

$stm->execute(array(":user_id" => $user_id, ":hash" => $hash, ":expire" => $future, ":hash2" => $hash));

This modification ensures that each value being bound has a unique parameter marker, resolving the "Invalid parameter number" error.

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