问PHP将多维数组压缩成字符串

EN

$input_array = array(
    'one' => array(
            'two' => '3',
            'four' => array(5,6,7)
        ),
    'eight' => array(
            'nine' =>  array(
                    'ten' => '11'
                )
        )

);

one/two:3 
one/four/0:5 
one/four/1:6 
one/four/2:7 
eight/nine/ten:11

function flatten($array) {
    if (is_array($array)) {
        //get the key and value pair of the array
        foreach ($array as $key => $value) {

            if (is_array($value)) {
                echo $key.'/';
            } else {
                echo $key.":".$value."<br/>\n";
            }

            flatten($value);
        }

    } else {
        return false;
    }


}

flatten($input_array);

one/two:3
four/0:5
1:6
2:7
eight/nine/ten:11