php 数组组合

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

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

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

$set = array('a','b','c','d');$arr=array();for($j=0;$j<sizeof($set);$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)