Calling PHP Function through JavaScript with Parameter

I have a function in a separate PHP page to add information to a MySql database. However if I want to pass in a paramater which is only available in my JavaScript file.

PHP Function in ModelBrowse.php

function databaseAdd($lockval)
{
    include_once('../dbConnect.php'); 

    $con = connect();
        if (!$con) {
            trigger_error(mysqli_error($con), E_USER_ERROR);
            die('Could not connect: ' . mysqli_error($con));
        }
        if ($lockval = "locked")
        {
        $sql = "INSERT INTO model(lock) VALUES ('lock')";
        }

        if ($lockval = "unlocked")
        {
        $sql = "INSERT INTO model(lock) VALUES ('unlock')";
        }


        mysqli_query($con, $sql)

        mysqli_close($con);
}

I want to call databaseAdd in my JavaScript file. I know I must use AJAX but I am confused on how I must do this.

via Chebli Mohamed