php 数组组合

$set = array('a','b','c','d');

该如何把数组组合,输出的结果是
a
b
c
b
ab
ac
ad
bc
bd

回复讨论(解决方案)

$set = array('a','b','c','d');$res = $set;for($i=0, $p=1; $iArray  
 (  
     [0] => a  
     [1] => b  
     [2] => c  
     [3] => d  
     [4] => ab  
     [5] => bc  
     [6] => cd  
 )  
  
   
$set = array('a','b','c','d');$res = $set;for($i=0, $p=1; $iArray   
 (   
     [0] => a   
     [1] => b   
     [2] => c   
     [3] => d   
     [4] => ab   
     [5] => bc   
     [6] => cd   
 )    
 版主这个输出的和楼主的不一样啊，我没太搞懂楼主到底是要怎么组合输出这个数组,我的解决方法如下，这里不用输出cd就可以了  
  

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)
  
  
$set = array('a','b','c','d');$arr=array();for($j=0;$j$v){    for($i=$k;$i  
Array(    [0] => a    [1] => b    [2] => c    [3] => d    [4] => ab    [5] => ac    [6] => ad    [7] => bc    [8] => bd    [9] => cd)