MySQL表到JSON有奇怪的输出[重复]

I've this MySQL table:

TABLE `table1` (
  `ID` int(11) NOT NULL,
  `First` varchar(30) DEFAULT NULL,
  `Second` varchar(30) DEFAULT NULL,
)

And this PHP code that is used for query the table and encode its contents into a JSON object:

<?php
/* Connection stuffs*/

$query = " SELECT * FROM table1;";
$results = mysql_query($query);
$stuff = array();
    while($row = mysql_fetch_array($results))
        array_push($stuff,$row);
$ja = json_encode($stuff);
echo $ja;
?>

Now, the code is working but I get a strange output (I'm only posting one row for question's readability but the others are the same) :

{
    "0": "1",
    "ID": "1",
    "1": "ivh",
    "First": "ivh",
    "2": "gyt",
    "Second": "gyt"
}

My question is: Why echo $ja; doesn't print this?

{
        "ID": "1",
        "First": "ivh",
        "Second": "gyt"
    }

Where do "0","1","2" come from? Furthermore the "0" 's content is the same of ID, as well as 1-First and 2-Second. There kind of a relationship between the MySQL column number and the $ja contents.

I've also tried to use this query:

$query = " SELECT ID,First,Second FROM table1;";

But the results are the same. Could someone help me? Thanks!

</div>

Suggest you to use mysql_fetch_assoc() or mysql_fetch_array($results, MSSQL_ASSOC). It will return only columns instead of being duplicate

$query = " SELECT * FROM table1;";
$results = mysql_query($query);
$stuff = array();
while($row = mysql_fetch_array($results, MSSQL_ASSOC))
{
    array_push($stuff,$row);
}
$ja = json_encode($stuff);
echo $ja;