php array help

Hi

This is the array im working on

$x = 0;
while($row = mysql_fetch_object($sql_result) )
{
$json[$x] = array    (
   $json[$x] = array    (   
                            'id' => $row->fid,
                            'rel' => $row->ftype,							
                        ),
			
			"data" => $row->ftitle,
			"state" => ""
);  
$x++;

}
echo  json_encode($json);

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this out put is like

[{"0":{"id":"3","rel":"file"},"data":"file1.doc","state":""},{"0":{"id":"4","rel":"file"},"data":"filetest.doc","state":""}]

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i have no idea why "0" appear on output.

is there way to replace "0" with "attr" ?

any help would be great.

Thanks