以此尝试

$result=mysql_query($sql, $con);
$json = array();
while($row = mysql_fetch_array($result))     
 {
    $json[]= array(
       'name' => $row['name'],
     'password' => $row['password']
    );
}

$jsonstring = json_encode($json);
 echo $jsonstring;

当您可以使用mysqli或PDO时，不建议使用mysql

And mysql is deprecated, when you can use mysqli or PDO