php 중복 문자 제거

$arr_a = explode(",", $a);

$arr_b = explode(",", $c);

 

//여집합 

$arr_c = array_merge(
            array_diff($arr_a, $arr_b),         // 1
            array_diff($arr_b, $arr_a)          //4
        );                              

 //  $arr_c = 1  4

 

echo implode(",", $arr_c);

//result = 1,4

 

//교집합은

$arr_d = array_intersect($arr_a, $arr_b);  //2, 3

 

//합집합은

$arr_e = array_merge(
            array_intersect($arr_a, $arr_b),   //2, 3
            array_diff($arr_a, $arr_b),         // 1
            array_diff($arr_b, $arr_a)          //4
        );   //2, 3, 1, 4