[PHP][MySQL] PDO Search with multiple where doesent work

Question

This code works:

function readSearchComputers(string $searchterm)
{
    $db_connect = db_connect();
    $statement = $db_connect->prepare("select * from db_computer WHERE computerIdentify like CONCAT('%', :searchterm, '%') ORDER BY systemLastOnlineSeen DESC");
    $statement->execute(array($searchterm));
    return $statement->fetchALL(PDO::FETCH_ASSOC);
}

This code also works:

function readSearchComputers(string $searchterm)
{
    $db_connect = db_connect();
    $statement = $db_connect->prepare("select * from db_computer WHERE computerSerial like CONCAT('%', :searchterm, '%') ORDER BY systemLastOnlineSeen DESC");
    $statement->execute(array($searchterm));
    return $statement->fetchALL(PDO::FETCH_ASSOC);
}

But this code failed and I have no idea, what I can do now. Anyone could help please?

function readSearchComputers(string $searchterm)
{
    $db_connect = db_connect();
    $statement = $db_connect->prepare("select * from db_computer WHERE computerIdentify like CONCAT('%', :searchterm, '%') || computerSerial like CONCAT('%', :searchterm, '%') ORDER BY systemLastOnlineSeen DESC");
    $statement->execute(array($searchterm));
    return $statement->fetchALL(PDO::FETCH_ASSOC);
}

The error is:

Fatal error: Uncaught PDOException: SQLSTATE[HY093]: Invalid parameter number in /.../functions.inc.php:74 Stack trace: #0 /.../functions.inc.php(74): PDOStatement->execute(Array) #1 /.../show.php(116): readSearchComputers('What I searched for') #2 {main} thrown in /.../functions.inc.php on line 74