Sorting Multidimensional Arrays by Value in PHP

Introduction

Sorting multidimensional arrays is a common task in PHP programming, especially when dealing with complex data structures. In this article, we will explore how to sort a multidimensional array based on a specific key within its inner arrays. We’ll demonstrate the process using a simple example and explain the steps involved in achieving the desired sorting.

Example Scenario

Consider a multidimensional array that contains elements, each consisting of a ‘position’ value. Our objective is to sort this array in ascending order based on the ‘position’ value.

$array = [
    ['position' => 5],
    ['position' => 3],
    ['position' => 4],
];

Sorting Algorithm

To accomplish the task of sorting the multidimensional array, we need to define a custom comparison function and then use PHP’s usort() function, which sorts an array using a user-defined comparison function.

1. Define a Custom Comparison Function

The first step is to create a function that will compare the ‘position’ values of two elements in the array. The custom comparison function will return a negative value if the first element’s ‘position’ is smaller than the second element’s ‘position’, a positive value if the first element’s ‘position’ is greater, and zero if both ‘position’ values are equal.

function sortByPosition($a, $b) {
    return $a['position'] - $b['position'];
}

2. Use usort() with the Custom Comparison Function

Once the custom comparison function is defined, we can utilize the usort() function to sort the array based on the ‘position’ value. The usort() function will take the array to be sorted as the first argument and the name of the custom comparison function as the second argument.

usort($array, 'sortByPosition');

Final Output

After sorting the array using the usort() function, we can print the result to verify the sorting order.

print_r($array);

The output will be:

Array
(
    [0] => Array
        (
            [position] => 3
        )

    [1] => Array
        (
            [position] => 4
        )

    [2] => Array
        (
            [position] => 5
        )
)

Conclusion

Sorting multidimensional arrays in PHP can be achieved by defining a custom comparison function and then using the usort() function. This process allows us to sort the array based on specific keys within its inner arrays, providing a versatile way to organize complex data structures in our PHP applications.