How to print the values at each level in a nested array in php

Question

I have a nested array containing numbers on multiple levels. The array key “number” will be holding an integer corresponding to that level and the key 'sub_level' will be holding an array with the same structure. Each level may or may not have a sub_level.

Sample Input

[
    0 => [
            'number' => 72,
            'sub_level' => [
                    'number' => 53,
                    'sub_level' => [
                            'number' => 49
                        ]
              ]
        ],
    1 => [
            'number' => 92,
            'sub_level' => [
                    'number' => 74
                ]
        ],
    2 => [
            'number' => 7
        ]
];

Sample o/p: 
Level 0: 72,92,7
Level 1: 53,74
Level 2: 49-->

You'd write a recursive function I guess. What have you tried? — Jonnix
– Jonnix, Commented Oct 14, 2020 at 11:00

Nick · Accepted Answer · 2020-10-14 21:33:11Z

This is easily solved with a recursive function, using array_column to get the number values at each level, and again to pass the sub_level to the recursive call:

function print_numbers($array, $level = 0) {
    if (empty($array)) return;
    echo "level $level: " . implode(',', array_column($array, 'number')) . "\n";
    print_numbers(array_column($array, 'sub_level'), $level+1);
}

print_numbers($input);

Output:

level 0: 72,92,7
level 1: 53,74
level 2: 49

If you want to extract all the numbers into a multi-dimensional array indexed by the level, you can modify the above function to return the values rather than echo them:

function save_numbers($array) {
    if (empty($array)) return array();
    return array_merge(array(array_column($array, 'number')), save_numbers(array_column($array, 'sub_level')));;
}

$out = save_numbers($input);
print_r($out);

Output:

Array
(
    [0] => Array
        (
            [0] => 72
            [1] => 92
            [2] => 7
        )
    [1] => Array
        (
            [0] => 53
            [1] => 74
        )
    [2] => Array
        (
            [0] => 49
        )
)

Demo on 3v4l.org

Al-Amin · Accepted Answer · 2020-10-14 20:43:14Z

1

To solve this type of problem recursive is great.I have pushed the same levels in the $higher variable and the lower levels in the $lower variable. Then called the $lower var recursively.

function print_levels($array, $level = 0 ) {
    foreach ($array as $key1 => $value1) {
        foreach ($value1 as $key2 => $value2 ) {
            if( is_array( $value2 ) ){
                $lower [] = $value2;
            }else{
                $higher [] = $value2;
            }
        }
    }
    echo 'level '.$level. ': '.  implode( ',', $higher ) . '<br>';
    if( ! isset($lower) )
        return;
    else
        print_levels($lower, ++$level);
}

answered Oct 14, 2020 at 20:43

Al-Amin

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Comments

jspit · Accepted Answer · 2020-10-14 12:49:55Z

0

A solution with iterators that deliver the result as a multi-dimensional array. The implode function can be used to generate a list of the form 72,92,7.

$level = [];
$it =  new RecursiveIteratorIterator(new RecursiveArrayIterator($array));
foreach($it as $key => $element) {
  if($key == 'number'){
    $level[$it->getDepth()][] = $element;
  }
}

Result $level:

array (
  1 => 
  array (
    0 => 72,
    1 => 92,
    2 => 7,
  ),
  2 => 
  array (
    0 => 53,
    1 => 74,
  ),
  3 => 
  array (
    0 => 49,
  ),
)

answered Oct 14, 2020 at 12:49

jspit

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