多维数组的递归？

Question

I have array like this:

$array = [
    'Category 1',
    'Category 2',
    [
        [
            'SubCategory 1',
            'SubCategory 2'
        ],
        [
            'SubCategory 3',
            'SubCategory 4',
            [
                [
                    'SubSubCategory 1',
                    'SubSubCategory 2'
                ]
            ]
        ],
        [
            'SubCategory 4',
            'SubCategory 5',
            [
                [
                    'SubSubCategory 3',
                    'SubSubCategory 4'
                ]
            ]
        ]
    ]
];

And i try do recursion:

function recursive($array)
{
    foreach($array as $key => $val) {
        if(is_array($val)) {
            recursive($val);
        }
        echo $val;
    }
}

It throws an notice "Notice: Array to string conversion" because

   [2] => array(
        [0] => array(..)
        [1] => array(..)
        ..
    );

And also echo Array

In this case, when the array has such a layout. How can I avoid that notice?

Answer 1

You only want to echo the value if it is not an array, so just add an else.

function recursive($array)
{
    foreach($array as $key => $val) {
        if(is_array($val)) {
            recursive($val);
        } else {
            echo $val;
        }
    }
}