Php create multidimensional array in loop

I am trying to create a multidimensional array in PHP using a foreach loop. Here is the code thus far:

$levels = array('low', 'medium', 'high');
$attributes = array('fat', 'quantity', 'ratio', 'label');

foreach ($levels as $key => $level):
       foreach ($attributes as $k =>$attribute):
             $variables[] = $attribute . '_' . $level;
       endforeach;
endforeach;

echo '<pre>' . print_r($levels,1) . '</pre>';   
echo '<pre>' . print_r($variables,1) . '</pre>';    

The output from this code is a single dimension array; however, that is not the intent. The desired array should look like this:

How should the code be modified to achieve the goal?

asked Aug 8, 2013 at 20:39

1

You're aaalmost there. Just add the level to the array creation :)

$levels = array('low', 'medium', 'high');
$attributes = array('fat', 'quantity', 'ratio', 'label');

foreach ($levels as $key => $level):
       foreach ($attributes as $k =>$attribute):
             $variables[$level][] = $attribute . '_' . $level; // changed $variables[] to $variables[$level][]
       endforeach;
endforeach;

echo '<pre>' . print_r($levels,1) . '</pre>';   
echo '<pre>' . print_r($variables,1) . '</pre>';  

Output

Array
(
    [low] => Array
        (
            [0] => fat_low
            [1] => quantity_low
            [2] => ratio_low
            [3] => label_low
        )

    [medium] => Array
        (
            [0] => fat_medium
            [1] => quantity_medium
            [2] => ratio_medium
            [3] => label_medium
        )

    [high] => Array
        (
            [0] => fat_high
            [1] => quantity_high
            [2] => ratio_high
            [3] => label_high
        )

)

answered Aug 8, 2013 at 20:42

JimLJimL

2,4711 gold badge18 silver badges19 bronze badges

1

$levels = ['low', 'medium', 'high'];
$attributes = ['fat', 'quantity', 'ratio', 'label'];

$result = [];
foreach ($levels as $level) {
    $result[$level] = [];
    foreach ($attributes as $attribute) {
        $result[$level][] = $attribute . '_' . $level;
    }
}

var_dump($result);

answered Aug 8, 2013 at 20:44

Tomasz KowalczykTomasz Kowalczyk

10.4k6 gold badges54 silver badges66 bronze badges

4

$levels = array('low', 'medium', 'high');
$attributes = array('fat', 'quantity', 'ratio', 'label');

foreach ($levels as $key => $level){
    foreach ($attributes as $k =>$attribute){
             $variables[$level][] = $attribute . '_' . $level;
   }
}

print_r($variables);

http://codepad.viper-7.com/xlvZ2W

answered Aug 8, 2013 at 20:46

In the previous pages, we have described arrays that are a single list of key/value pairs.

However, sometimes you want to store values with more than one key. For this, we have multidimensional arrays.

PHP - Multidimensional Arrays

A multidimensional array is an array containing one or more arrays.

PHP supports multidimensional arrays that are two, three, four, five, or more levels deep. However, arrays more than three levels deep are hard to manage for most people.

The dimension of an array indicates the number of indices you need to select an element.

• For a two-dimensional array you need two indices to select an element
• For a three-dimensional array you need three indices to select an element

PHP - Two-dimensional Arrays

A two-dimensional array is an array of arrays (a three-dimensional array is an array of arrays of arrays).

First, take a look at the following table:

We can store the data from the table above in a two-dimensional array, like this:

$cars = array (
  array("Volvo",22,18),
  array("BMW",15,13),
  array("Saab",5,2),
  array("Land Rover",17,15)
);

Now the two-dimensional $cars array contains four arrays, and it has two indices: row and column.

To get access to the elements of the $cars array we must point to the two indices (row and column):

Example

<?php
echo $cars[0][0].": In stock: ".$cars[0][1].", sold: ".$cars[0][2].".<br>";
echo $cars[1][0].": In stock: ".$cars[1][1].", sold: ".$cars[1][2].".<br>";
echo $cars[2][0].": In stock: ".$cars[2][1].", sold: ".$cars[2][2].".<br>";
echo $cars[3][0].": In stock: ".$cars[3][1].", sold: ".$cars[3][2].".<br>";
?>

Try it Yourself »

We can also put a for loop inside another for loop to get the elements of the $cars array (we still have to point to the two indices):

Example

<?php
for ($row = 0; $row < 4; $row++) {
  echo "<p><b>Row number $row</b></p>";
  echo "<ul>";
  for ($col = 0; $col < 3; $col++) {
    echo "<li>".$cars[$row][$col]."</li>";
  }
  echo "</ul>";
}
?>

Try it Yourself »

Complete PHP Array Reference

For a complete reference of all array functions, go to our complete PHP Array Reference.

The reference contains a brief description, and examples of use, for each function!

How do you loop through a multidimensional array in PHP?

How to define multiple array in PHP?

How can we store multidimensional array in database using PHP?

What is multidimensional array example?