How to Efficiently Search for Key-Value Pairs in PHP's Multidimensional Arrays?

Searching for Key-Value Pairs in Multidimensional Arrays in PHP

Introduction:

Finding specific subarrays based on key-value matches within multidimensional arrays can be challenging, especially when the array's depth is unknown. This article explores a recursive approach to efficiently accomplish this search operation.

Function Definition:

function search($array, $key, $value)
{
    // Initialize an empty results array
    $results = array();

    // Check if the current element is an array
    if (is_array($array)) {
        // If the current element matches the key-value pair, add it to the results
        if (isset($array[$key]) && $array[$key] == $value) {
            $results[] = $array;
        }

        // Recursively search through each subarray
        foreach ($array as $subarray) {
            $results = array_merge($results, search($subarray, $key, $value));
        }
    }

    // Return the accumulated results
    return $results;
}

Example:

Consider the following multidimensional array:

$arr = array(
    0 => array('id' => 1, 'name' => "cat 1"),
    1 => array('id' => 2, 'name' => "cat 2"),
    2 => array('id' => 3, 'name' => "cat 1")
);

When searching for the key-value pair 'name' => 'cat 1', the function will return:

array(
    0 => array('id' => 1, 'name' => "cat 1"),
    1 => array('id' => 3, 'name' => "cat 1")
);

Performance Considerations:

For scenarios where efficiency is paramount, an alternative approach is available:

function searchOptimized($array, $key, $value)
{
    $results = array();
    searchOptimized_r($array, $key, $value, $results);
    return $results;
}

function searchOptimized_r($array, $key, $value, &$results)
{
    if (!is_array($array)) {
        return;
    }

    if (isset($array[$key]) && $array[$key] == $value) {
        $results[] = $array;
    }

    foreach ($array as $subarray) {
        searchOptimized_r($subarray, $key, $value, $results);
    }
}

In this optimized version, the search results are accumulated directly in the temporary $results array, eliminating the need for array merging. By specifying the pass-by-reference in the call to searchOptimized_r, this version maintains high performance while preserving compatibility with older PHP versions.

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