Php post and edit checkbox?

Current Code

<?php

if(!empty($_POST['submit'])){

    $var['text'] = $_POST['text'];
    $var['checkbox'] = ($_POST['checkbox']) ? 'yes' : 'no';

    foreach($var as $key => $value){

        $query = 'UPDATE configs SET value = :value WHERE config = :key';
        $update = $db->prepare($query);
        $update->bindParam(':value', $value, PDO::PARAM_STR);
        $update->bindParam(':key', $key, PDO::PARAM_STR);
        $update->execute();

    }

}else{

    $var['text'] = 'Testing text';// configs['text']; from db //
    $var['checkbox'] = 'no';// configs['checkbox']; from db //

}

$smarty->assign('var', $var);
$smarty->display('test.tpl');

$db = NULL;

?> 

This is What i looking for ...................................

$var['text'] = isset($_POST['text']) ? $_POST['text'] : $configs['text'];// $configs['text']; from db //

If submit button clicked then checkbox values yes or no else show db result

$var['checkbox'] = '???????????????????????';// $configs['checkbox']; from db //