json_encode แต่ข้อมูลภาษาไทยออกมาเป็นภาษาแปลกๆ ใครพอมีวิธีแก้มั้งคับ

<?

class mysql2json{

 function getJSON($resultSet,$affectedRecords){
 $numberRows=0;
 $arrfieldName=array();
 $i=0;
 $json="";
	//print("Test");
 	while ($i < mysql_num_fields($resultSet))  {
 		$meta = mysql_fetch_field($resultSet, $i);
		if (!$meta) {
		}else{
		$arrfieldName[$i]=$meta->name;
		}
		$i++;
 	}
	 $i=0;
	  $json="[\n";
	while($row=mysql_fetch_array($resultSet, MYSQL_NUM)) {
		$i++;
		//print("Ind ".$i."-$affectedRecords<br>");
		$json.="{\n";
		for($r=0;$r < count($arrfieldName);$r++) {
			$json.="\"$arrfieldName[$r]\" :	\"$row[$r]\"";
			if($r < count($arrfieldName)-1){
				$json.=",\n";
			}else{
				$json.="\n";
			}
		}
	
		if($i!=$affectedRecords){
		 	$json.="\n},\n";
		}else{
		 	$json.="\n}\n";
		}	
	}
	$json.="\n]";
	return $json;
 }
}
?>

<?
	require("mysql2json.class.php");
	$hostname_connection = "localhost";
	$database_connection = "XXXX";
	$username_connection = "XXXX";
	$password_connection = "XXXX";
	$connection = mysql_connect($hostname_connection, $username_connection, $password_connection) or trigger_error(mysql_error(),E_USER_ERROR); 
	mysql_query("SET character_set_results=utf8");
	mysql_query("SET character_set_client=utf8");
	mysql_query("SET character_set_connection=utf8");
	mysql_select_db($database_connection, $connection);
	
	
	$query="SELECT XXXXX FROM XXX ORDER BY XXXXX ASC ";
	$result=mysql_query($query,$connection);
	$num=mysql_affected_rows();
	
	$json=new mysql2json;
	$data=$json->getJSON($result,$num);
	echo $data;
?>

<?
mysql_query("SET NAMES UTF8");


$mysqlstatement="SELECT*FROM books ";
$result=mysql_query($mysqlstatement,$con);

				while($member= mysql_fetch_assoc($result)){
			
				
				$output[]=$member;
		
				
				}
		
				print(json_encode($output));

				mysql_close($con);
				
?>

header("Content-Type: text/html; charset=UTF-8");
   $a = array('ฟดกหด');
   echo json_encode($a, JSON_HEX_TAG | JSON_UNESCAPED_UNICODE);