在EXTRACT（）查询中使用PDO参数

I'm creating a function to get stats on different players from a database and I need to be able to specify the timescale the stats are for as one of the function's variables - it'll be something like 'month' or 'year'.

I've had some success in creating SQL queries using EXTRACT() to compare the record timestamp with the current time but I can't seem to use a PDO variable to change this with each function call.

Any ideas what I'm doing wrong? Or is this just a limitation of bindParam()?

function get_player_stats($player_id, $timescale) {
    global $pdo;

    $query = $pdo->prepare('
        SELECT count(results.winner)
        FROM results
        WHERE results.winner = :player_id
        AND EXTRACT(:timescale FROM results.date) = EXTRACT(:timescale FROM NOW())
        LIMIT 1
    ');

    $query->bindParam(':player_id', $player_id);

    if ($timescale = 'this_month') {
        $query->bindParam(':timescale','YEAR_MONTH');
    }

    else if ($timescale = 'this_year') {
        $query->bindParam(':timescale','YEAR');
    }

    $query->execute();

    return $query->fetchAll(PDO::FETCH_OBJ);
}

P.S. It's a MySQL database

I see two problems here:

1. The EXTRACT() function doesn't expect a string but an identifier. You cannot use bind parameters to provide identifiers (such as table names).

2. Repeating place-holders is not supported by all PDO drivers and modes thus it's discouraged.

You'll have to inject the value into the SQL code with your favourite string manipulation technique.

From the PHP PDO docs:

You cannot use a named parameter marker of the same name twice in a prepared statement.

I read somewhere that old versions of PHP allowed you to put one placeholder in multiple parts of the query, however this feature has been removed in newer versions of PHP. You'll need to give each placeholder different names in your query.