从外部MySQL数据库获取JSON错误？

i am using this tutorial and i dont know what is error is this

    <?php
header('Content-type: application/json');  // this is the magic that sets responseJSON

// Connecting, selecting database
$link = mysql_connect($dbhost, $dbuser, $dbpass)
    or die('Could not connect: ' . mysql_error());
mysql_select_db($dbname) or die('Could not select database');

switch($_POST['op']) {
    case 'getAllRecords': {
        $table = $_POST['table'];
        $query = sprintf("SELECT * FROM %s", mysql_real_escape_string($table));
        // Performing SQL query
        $result = mysql_query($query) or die('Query failed: ' . mysql_error());
        $all_recs = array();
        while ($line = mysql_fetch_array($result, MYSQL_ASSOC)) {
            $all_recs[] = $line;
        }
        break;
    }
}

echo json_encode($all_recs);

// Free resultset
mysql_free_result($result);

// Closing connection
mysql_close($link);
?>

error is :- null
Warning: mysql_free_result(): supplied argument is not a valid MySQL result resource in /home/ajay/public_html/mapleleafrealities.com/test.php on line 26

This is Example

My Error

if you have any simple example of getting json from external db please give me link or code

The op POST parameter is not "getAllRecords", so you're trying to encode something that doesn't exist, and free a result that was never taken. Try putting them inside.