PHP Tutorial: Using array_walk_recursive() to Process Each Element in a Multidimensional Array

Introduction to PHP's array_walk_recursive() Function

array_walk_recursive() is a powerful built-in PHP function that recursively traverses every element in a multidimensional array and applies a specified callback function to it. It is ideal for scenarios where uniform processing of complex array structures is needed.

Creating a Sample Multidimensional Array

To demonstrate the usage of array_walk_recursive(), let's first define a multidimensional array containing student information, including their names, ages, and scores:

$students = array(
    array(
        'name' => 'Zhang San',
        'age' => 18,
        'scores' => array(80, 85, 90),
    ),
    array(
        'name' => 'Li Si',
        'age' => 19,
        'scores' => array(75, 78, 82),
    ),
    array(
        'name' => 'Wang Wu',
        'age' => 20,
        'scores' => array(90, 95, 88),
    ),
);

Defining a Callback Function to Calculate Average Scores

Next, we write a callback function that checks if the key is scores. If so, it calculates the average score and appends this value into the scores array:

function calculateAverage(&$value, $key)
{
    if ($key === 'scores') {
        $average = array_sum($value) / count($value);
        $value['average'] = $average;
    }
}

Using array_walk_recursive() to Traverse and Process the Array

We use array_walk_recursive() to recursively traverse the multidimensional array and apply the callback function to each element:

<span class="fun">array_walk_recursive($students, 'calculateAverage');</span>

This adds an average key to each student's scores array, storing their average score.

Verifying the Result

By printing the modified array, we can clearly see the average scores have been added correctly:

<span class="fun">print_r($students);</span>

Sample output:

Array
(
    [0] => Array
        (
            [name] => Zhang San
            [age] => 18
            [scores] => Array
                (
                    [0] => 80
                    [1] => 85
                    [2] => 90
                    [average] => 85
                )
        )
    [1] => Array
        (
            [name] => Li Si
            [age] => 19
            [scores] => Array
                (
                    [0] => 75
                    [1] => 78
                    [2] => 82
                    [average] => 78.33333333333333
                )
        )
    [2] => Array
        (
            [name] => Wang Wu
            [age] => 20
            [scores] => Array
                (
                    [0] => 90
                    [1] => 95
                    [2] => 88
                    [average] => 91
                )
        )
)

Conclusion

This article explained how to use PHP's array_walk_recursive() function to recursively traverse multidimensional arrays and process their elements flexibly with callback functions. This approach enables developers to efficiently handle nested array data to meet complex application needs.