静态变量连接先前的结果值php

Question

我具有此递归函数，可将所有中间类别从第n个孩子获取到父类别。 但是，当id更改时，变量$ cats将串联到前一个结果。 在执行第二个第n个子ID之前，我不希望它为null。 见下面的代码

function find_parent($cat_id,$conn){
    static $cats;
    if ($cat_id > 0){
        $q = mysqli_query($conn,'SELECT pw_cat_pid FROM pw_categories WHERE pw_cat_id = ' . $cat_id) or die(mysqli_error($conn));
        $r = mysqli_fetch_assoc($q);
  $cats[] = $cat_id;
  find_parent($r["pw_cat_pid"],$conn);
    }
 return $cats;
}


$sub_cat = array(5,122);

foreach($sub_cat as $value)
{
 $cat = find_parent($value);
 print_r($cat);
} 


It showed below result:

If $sub_cat = 5
 Array ( [0] => 5 [1] => 3 [2] => 1 ) 

If $sub_cat = 122

Array ( [0] => 5 [1] => 3 [2] => 1 [3] => 121 [4] => 97 [5] => 1 )

Answer 1

不要使用静态变量，请使用by-refrence实现目标：

   function find_parent($cat_id,$conn, &$cats=array()){
        if ($cat_id > 0){
            $q = mysqli_query($conn,'SELECT pw_cat_pid FROM pw_categories WHERE pw_cat_id = ' . $cat_id) or die(mysqli_error($conn));
            $r = mysqli_fetch_assoc($q);
      $cats[] = $cat_id;
      find_parent($r["pw_cat_pid"],$conn,$cats);
        }
     return $cats;
    }


    $sub_cat = array(5,122);

    foreach($sub_cat as $value)
    {
     $cat = find_parent($value,$conn);
     echo "<pre>";
    print_r($cat);

    }