本文實例講述了PHP笛卡爾積實現算法。分享給大家供大家參考，具體如下：

<?php
$arr = array(array(1,3,4,5),array(3,5,7,9),array(76,6,1,0));
/**
** 實現二維數組的笛卡爾積組合
** $arr 要進行笛卡爾積的二維數組
** $str 最終實現的笛卡爾積組合,可不寫
** @return array
**/
function cartesian($arr,$str = array()){
  //去除第一個元素
  $first = array_shift($arr);
  //判斷是否是第一次進行拼接
  if(count($str) > 1) {
    foreach ($str as $k => $val) {
      foreach ($first as $key => $value) {
        //最終實現的格式 1,3,76
        //可根據具體需求進行變更
        $str2[] = $val.','.$value;
      }
    }
  }else{
    foreach ($first as $key => $value) {
      //最終實現的格式 1,3,76
      //可根據具體需求進行變更
      $str2[] = $value;
    }
  }
  //遞歸進行拼接
  if(count($arr) > 0){
    $str2 = cartesian($arr,$str2);
  }
  //返回最終笛卡爾積
  return $str2;
}
$cartesian_product = cartesian($arr);
print_r($cartesian_product);
?>

最終輸出格式

Array
(
    [0] => 1,3,76
    [1] => 1,3,6
    [2] => 1,3,1
    [3] => 1,3,0
    [4] => 1,5,76
    [5] => 1,5,6
    [6] => 1,5,1
    [7] => 1,5,0
    [8] => 1,7,76
    [9] => 1,7,6
    [10] => 1,7,1
    [11] => 1,7,0
    [12] => 1,9,76
    [13] => 1,9,6
    [14] => 1,9,1
    [15] => 1,9,0
    [16] => 3,3,76
    [17] => 3,3,6
    [18] => 3,3,1
    [19] => 3,3,0
    [20] => 3,5,76
    [21] => 3,5,6
    [22] => 3,5,1
    [23] => 3,5,0
    [24] => 3,7,76
    [25] => 3,7,6
    [26] => 3,7,1
    [27] => 3,7,0
    [28] => 3,9,76
    [29] => 3,9,6
    [30] => 3,9,1
    [31] => 3,9,0
    [32] => 4,3,76
    [33] => 4,3,6
    [34] => 4,3,1
    [35] => 4,3,0
    [36] => 4,5,76
    [37] => 4,5,6
    [38] => 4,5,1
    [39] => 4,5,0
    [40] => 4,7,76
    [41] => 4,7,6
    [42] => 4,7,1
    [43] => 4,7,0
    [44] => 4,9,76
    [45] => 4,9,6
    [46] => 4,9,1
    [47] => 4,9,0
    [48] => 5,3,76
    [49] => 5,3,6
    [50] => 5,3,1
    [51] => 5,3,0
    [52] => 5,5,76
    [53] => 5,5,6
    [54] => 5,5,1
    [55] => 5,5,0
    [56] => 5,7,76
    [57] => 5,7,6
    [58] => 5,7,1
    [59] => 5,7,0
    [60] => 5,9,76
    [61] => 5,9,6
    [62] => 5,9,1
    [63] => 5,9,0
)

小編這里參考前面一篇《JavaScript笛卡爾積超簡單實現算法》，給出一個php計算笛卡爾積的超簡單算法示例如下：

<?php
function cartesian($arr1,$arr2){
  $relarr = array();
  foreach($arr1 as $v1){
    foreach($arr2 as $v2){
      array_push($relarr,$v1.",".$v2);
    }
  }
  return $relarr;
}
//用法示例
$a = array('1','2','3');
$b = array('a','b',c);
print_r(cartesian($a,$b));
?>

運行結果：

Array
(
    [0] => 1,a
    [1] => 1,b
    [2] => 1,c
    [3] => 2,a
    [4] => 2,b
    [5] => 2,c
    [6] => 3,a
    [7] => 3,b
    [8] => 3,c
)

希望本文所述對大家PHP程序設計有所幫助。