Why Does PDO Throw 'SQLSTATE[HY093]: Invalid Parameter Number' and How Can I Fix It?

SQLSTATE[HY093]: Invalid Parameter Number with PDO

When attempting to execute a function, an error message indicating "SQLSTATE[HY093]: Invalid parameter number" may appear. This issue arises due to a misunderstanding of the behavior of named parameters with PDO.

The function you provided includes the following code:

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

When defining named parameters for a SQL statement, it's crucial to ensure that each unique parameter marker is used only once. However, in this case, ":hash" is used twice, which results in the error.

To resolve this issue, you need to assign a unique parameter marker for each value you pass to the statement when calling PDOStatement::execute():

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

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

The resulting SQL query will successfully insert or update the "persist" table without encountering the invalid parameter number error.

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