how to update datta using php update mysql code example

Example 1: live update mysql data in php

$(document).ready(function(){    
    loadstation();
});

function loadstation(){
    $("#station_data").load("station.php");
    setTimeout(loadstation, 2000);
}

Example 2: update php sql

$_old_username = "Randy";
$_new_username = $_POST["username"]; 

$_sql = "UPDATE user SET first_name = $_new_username WHERE first_name = $_old_username";