Php array combination

Php array combination $ set & nbsp; array (a, B, c, d); how to combine arrays, the output result is abcbabacadbcbd ------ solution ------------------ $ set & nbsp; array (a, B, c, d); $ res & nbsp; $ set; for ($ i0, php array combination
$ Set = array ('A', 'B', 'C', 'D ');

How to combine arrays? the output result is
A
B
C
B
AB
Ac
Ad
Bc
Bd
------ Solution --------------------

$set = array('a','b','c','d');
$res = $set;
for($i=0, $p=1; $i
   $res[] = $res[$i] . $set[$p];
}
print_r($res);

Array
(
[0] =>
[1] => B
[2] => c
[3] => d
[4] => AB
[5] => bc
[6] => cd
)

------ Solution --------------------
Reference:

$set = array('a','b','c','d');
$res = $set;
for($i=0, $p=1; $i
     $res[] = $res[$i] . $set[$p];
}
print_r($res);

Array
(
[0] =>
[1] => B
[2] => c
[3] => d
[4] => AB
[5] => bc
[6] => cd
)

The outputs of the moderator are different from those of the landlord. I am not sure how the moderator combines the outputs of this array. my solution is as follows: no cd output is needed here.

 $set = array('a','b','c','d');
$len = count($set);
$res = array();
for($i=0,$k=$len;$i<$len;$i++){
  $res[$i] = $set[$i];
  for($j=$i+1;$j<$len;$j++){
    $res[$k++] = $set[$i].$set[$j];
  }
}
ksort($res);
var_dump($res);
?>

array (size=10)
  0 => string 'a' (length=1)
  1 => string 'b' (length=1)
  2 => string 'c' (length=1)
  3 => string 'd' (length=1)
  4 => string 'ab' (length=2)
  5 => string 'ac' (length=2)
  6 => string 'ad' (length=2)
  7 => string 'bc' (length=2)
  8 => string 'bd' (length=2)
  9 => string 'cd' (length=2)

------ Solution --------------------

$set = array('a','b','c','d');
$arr=array();
for($j=0;$j
     $arr[]=$set[$j];
}
foreach($set as $k=>$v){
    for($i=$k;$i<=(3-$v);$i++){
        if($v==$set[$i]) continue;
        $arr[]=$v.$set[$i];
    }
}
print_r($arr);

Array
(
    [0] => a
    [1] => b
    [2] => c
    [3] => d
    [4] => ab
    [5] => ac
    [6] => ad
    [7] => bc
    [8] => bd
    [9] => cd
)