ฟังชั่น array_unique() ใน Internet explorer 8 ใช้ไม่ได้หรอค่ะ

$sql1="SELECT * FROM tb_acaserv
LEFT JOIN tb_user ON tb_acaserv.researcher_id = tb_user.user_id
LEFT JOIN personnel ON tb_user.user_name = personnel.CitizenCard
LEFT JOIN tb_budget ON tb_acaserv.budget_id = tb_budget.budget_no
LEFT JOIN perfix ON personnel.prefix = perfix.prefix_id
LEFT JOIN tb_key ON tb_acaserv.key_id = tb_key.id
LEFT JOIN tb_download ON tb_acaserv.file_ac = tb_download.dl_id";
					$result1 = mysql_query($sql1) ;
					$num_rows1 = mysql_num_rows($result1) ; 
					
					$sql_t="SELECT * FROM tb_type WHERE status = 2";
					$result_t = mysql_query($sql_t) ;
					$num_rows_t = mysql_num_rows($result_t) ; 
					for($j=0;$j<$num_rows_t;$j++){ 	 
						$t_id[$j] = mysql_result($result_t, $j, "type_id"); 
						$t_n[$j] = mysql_result($result_t, $j, "type_name"); 
						$count = 0;
						$count_dl = 0;
						$b = 0;
						for($i=0;$i<$num_rows1;$i++){ 	 
							$type_id[$i] = mysql_result($result1, $i, "type_id");
							if($type_id[$i] == $t_id[$j]){
								$re_t[$j][$b] = mysql_result($result1, $i, "acaserv_id");
								$b = $b + 1;
							}
							
							$dl_count = mysql_result($result1, $i, "dl_count");	// รหัสงานที่ถูกดาวน์โหลด
							$count_dl = $count_dl + $dl_count;
							$count = $count +1;			
							if($dl_count != 0){
								$down_id[$i] = mysql_result($result1, $i, "acaserv_id");
							}
							
							$p_count = mysql_result($result1, $i, "tb_acaserv.publicize_id");	// รหัสงานที่ได้เผยแพร่	
							if($p_count != ""){
								$p_id[$i] = mysql_result($result1, $i, "acaserv_id");
							}
							
							$budget_type[$i] = mysql_result($result1, $i, "budget_type");
							$budget = mysql_result($result1, $i, "budget");		// งบประมาณ
							$count_bg = $count_bg + $budget;
							$num_reh[$i] = mysql_result($result1, $i, "tb_acaserv.researcher_id");   // รหัสหัวหน้าโครงการ
							
						} // end for
					}// end for
				
					$clean = array_unique($num_reh);      //เอาค่าซ้ำออก
					$key = array_values($clean);              //print_r($key);echo "<br>";
					for($k=0;$k<count($key);$k++){		// รหัสหัวหน้าโครงการ 
						$sum_k = $sum_k."".$key[$k];
						if($k==(count($key)-1)){
							$sum_k = $sum_k."";
						}else{
							$sum_k = $sum_k.", ";
						}
					}
echo $sum_k;