มีปัญหา php json_encode ไม่แสดงค่าอะไรมาเลย บนhost แก้ยังไงครับ

$('#subject_stand').live('change',function(){
		var dataSet={
			ss_id:$(this).val(),
			type:"stand_metric"
					}
		$.getJSON('include/select_sara_unit.php',dataSet,function(data){
			if (data != null) {
				
			$('#stand_detail').html(data[0].stand_name).fadeIn();
			
			$('#subject_metric').html("<option value=''>กำหนดมาตรฐาน</option>");
			var index=0;
			
			//selectbox
			$.each(data[0].mlist_id, function(i,json){
				$('#subject_metric').append("<option value='"+data[0].mlist_id[index]+"'>ตัวชี้วัดที่ "+data[0].metric_no[index]+"</option>");
				index++;

			})//each
			}
			
		
		});//get
	});//change

$stand_detail="select * from tb_sara_join_stand ss,m_standard stand
						where ss.ss_id='".$_GET['ss_id']."'
						and stand.stand_id=ss.stand_id";
		$query_stand_de=mysql_query($stand_detail);
		$count_stand=mysql_num_rows($query_stand_de);
		
		$select_metric="select * from tb_metic_list ml,m_metric m
						where ml.ss_id='".$_GET['ss_id']."'
						and ml.metic_id=m.metric_id";
		$query_metric=mysql_query($select_metric);
		$count_metric=mysql_num_rows($query_metric);

                $row_detail=mysql_fetch_array($query_stand_de);
		$data_arr['stand_name']=$row_detail['stand_name'];
		
		
		$col=0;
		while($metric_row=mysql_fetch_array($query_metric))
		{
			
			$data_arr['mlist_id'][$col]=$metric_row['mlist_id'];
			
			$data_arr['metric_no'][$col]=$metric_row['metric_no'];
			$col++;
			
		}
		$arr[]=$data_arr;
		header('Content-type:application/json;charset=utf-8');
		echo json_encode($arr);