php recursive algorithm

Achieved through recursive factorial

function multi($n){

    IF ($ n-== 0) { 
        return. 1; // recursive termination 
    } 
    $ * Multi n-value = $ ($-n-. 1); 
    return $ value; 
} 

implement Fibonacci number recursively

Fib function (n-$) { 
    IF ($ $ n-n-== == 0 ||. 1) { 
        return. 1; // recursive termination 
    } 
    $ value = Fib (n--$. 1) Fib + (2-n-$); 
    $ value return; 
} 
echo Fib (. 6);

$ category = [ 
       [ 
           'ID' =>. 1, 
           'name' => 'men', 
           'PID' => 0, 
       ], 
       [ 
           'ID' => 2, 
            'name' => 'ladies', 
            'PID' => 0, 

       ], 
       [ 
           'ID' =>. 3, 
           'name' => 'men's jackets', 
           'PID' =>. 1, 
           ], 
         [ 
             'ID' =>. 4, 
             'name' => 'jacket', 
             'PID' =>. 3, 

         ], 
         [ 
             'ID' =>. 5, 
             'name '=>' cotton ', 
             ' PID '=>. 3, 
         ], 
];

Get all the subclasses of the parent class ID by

function recursiveCategory($pid,$category){
    $data = [];
    foreach ($category as $item){
        if($item['pid']==$pid){
            $arr['id'] = $item['id'];
            $arr['name'] = $item['name'];
            $cate = recursiveCategory($item['id'],$category);
            if(!empty($cate)){
                $arr[] =$cate;
            }
            $data[] = $arr;
            unset($arr);
        }
    }
    return $data;
};

Get all of the parent class by subclass

function getCategoryByChild($childId,$category){
    $data = [];
    foreach ($category as $item){
        if($item['id'] == $childId){
            $arr['id'] =$item['id'];
            $arr['name']= $item['name'];
            if($item['pid']!=0){
                $arr[] = getCategoryByChild($item['pid'],$category);
            }
            $data[]=$arr;
        }
    }
    return $data;
}