Output the raw SQL of a PDO prepared statement

raw_query.php

<?php

/**
  Usage:
    $sql = "SELECT * FROM foo WHERE id=? AND name=? AND groupId=?";
    $stmt = $pdo->prepare($sql);
    $rawSQL = interpolateQuery($sql, array($id, $name, $groupId);
    $stmt->execute(array($id, $name, $groupId));
**/
function interpolateQuery($query, $params) {
    $keys = array();

    # build a regular expression for each parameter
    foreach ($params as $key => $value) {
        if (is_string($key)) {
            $keys[] = '/:'.$key.'/';
        } else {
            $keys[] = '/[?]/';
        }
    }

    // Add quotes around strings.
    foreach ($params as &$param) {
        if (is_string($param)) {
            $param = "'$param'";
        }
    }

    $query = preg_replace($keys, $params, $query, 1, $count);

    #trigger_error('replaced '.$count.' keys');

    return $query;
}