<meta charset="utf-8">   
<?php 
function FetchRepeatMemberInArray($array) { 
    // 获取去掉重复数据的数组 
    $unique_arr = array_unique ( $array ); 
    // 获取重复数据的数组 
    $repeat_arr = array_diff_assoc ( $array, $unique_arr ); 
    return $repeat_arr; 
} 

// 测试用例 
$array = array ( 
        "apple", 
        "iphone", 
        "miui", 
        "apple", 
        "orange", 
        "orange"  
); 
$repeat_arr = FetchRepeatMemberInArray ( $array ); 
if($repeat_arr){
  print_r ( $repeat_arr ); 
}else{
  print_r ("没有重复数据"); 	
}
?>

array_unique() - 去除数组中重复的元素值

$a1="206,206,206,201,206,201";
//$array = explode(",", $a1);  //字符串组成数组
$array1=implode(",",array_unique(explode(",", $a1)));
 print_r($array1);

引用：http://www.jb51.net/article/39246.htm