Bdtjtk

So far, if I have to loop through a multidimensional array, I use a foreach loop for each dimension.

e.g for two dimensions

foreach($array as $key=>$value)

{

    foreach($value as $k2=>$v2)

    {

         echo

    }

}

What do I do when I don't know the depth of the array? ie the depth is variable.

The only thing I can think of is to code a whole stack of loops and to break the loop if the next value is not an array.This seems a little silly.

Is there a better way?

Yes, you can use recursion. Here's an example where you output all the elements in an array:

function printAll($a) {

  if (!is_array($a)) {

    echo $a, ' ';

    return;

  }



  foreach($a as $v) {

    printAll($v);

  }

}



$array = array('hello',

               array('world',

                     '!',

                     array('whats'),

                     'up'),

               array('?'));

printAll($array);

What you should always remember when doing recursion is that you need a base case where you won't go any deeper.

I like to check for the base case before continuing the function. That's a common idiom, but is not strictly necessary. You can just as well check in the foreach loop if you should output or do a recursive call, but I often find the code to be harder to maintain that way.

The "distance" between your current input and the base case is called a variant and is an integer. The variant should be strictly decreasing in every recursive call. The variant in the previous example is the depth of $a. If you don't think about the variant you risk ending up with infinite recursions and eventually the script will die due to a stack overflow. It's not uncommon to document exactly what the variant is in a comment before recursive functions.

You can use recursion for this problem:

Here is one example

$array = array(1 => array(1 => "a", 2 => array(1 => "b", 2 => "c", 3 => array(1 => "final value"))));



//print_r($array);



printAllValues($array);



function printAllValues($arr) {

    if(!is_array($arr)) {

        echo '<br />' . $arr;

        return;

    }

    foreach($arr as $k => $v) {

        printAllValues($v);

    }

}

It will use recursion to loop through array

It will print like

a

b

c

final value

Simple function inside array_walk_recursive to show the level of nesting and the keys and values:

array_walk_recursive($array, function($v, $k) {

                                 static $l = 0;

                                 echo "Level " . $l++ . ": $k => $vn";

                             });

Another one showing use with a reference to get a result:

array_walk_recursive($array, function($v) use(&$result) {

                                 $result = $v;

                             });

You can do the below function for loop-through-a-multidimensional-array-without-knowing-its-depth

// recursive function loop through the dimensional array

function loop($array){



    //loop each row of array

    foreach($array as $key => $value)

    {

         //if the value is array, it will do the recursive

         if(is_array($value) ) $array[$key] =  loop($array[$key]);



         if(!is_array($value)) 

         {

            // you can do your algorithm here

            // example: 

             $array[$key] = (string) $value; // cast value to string data type



         }

    }



    return $array;

}

by using above function, it will go through each of the multi dimensional array, below is the sample array you could pass to loop function :

 //array sample to pass to loop() function

 $data = [

  'invoice' => [

      'bill_information' => [

          'price' => 200.00,

          'quantity' => 5

      ],

      'price_per_quantity' => 50.00

  ],

  'user_id' => 20

];



// then you can pass it like this :

$result = loop($data);

var_dump($result);



//it will convert all the value to string for this example purpose

Based on previous recursion examples, here is a function that keeps an array of the path of keys a value is under, in case you need to know how you got there:

function recurse($a,$keys=array()) 

    {

        if (!is_array($a)) 

            {

                echo implode("-", $keys)." => $a <br>";

                return;

            }

        foreach($a as $k=>$v) 

            {

                $newkeys = array_merge($keys,array($k));

                recurse($v,$newkeys);

            }

    }





recurse($array);