How to Efficiently Find Subarrays Based on Key-Value Pairs in Multidimensional PHP Arrays?

Finding Subarrays Based on Key-Value Pairs in Multidimensional PHP Arrays

When traversing multidimensional arrays, it can be challenging to locate specific subarrays based on a key-value pair. However, there's an efficient way to do this recursively, regardless of the array's depth.

Function Implementation:

Let's create a function to search for subarrays meeting the specified conditions:

function search($array, $key, $value)
{
    $results = array();

    if (is_array($array)) {
        // Check if the current subarray matches
        if (isset($array[$key]) && $array[$key] == $value) {
            $results[] = $array;
        }

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

    return $results;
}

Usage Example:

Given the following sample array:

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

We can search for subarrays with the key 'name' and value 'cat 1':

$found = search($arr, 'name', 'cat 1');
print_r($found);

Output:

Array
(
    [0] => Array
        (
            [id] => 1
            [name] => cat 1
        )

    [1] => Array
        (
            [id] => 3
            [name] => cat 1
        )

)

Efficiency Considerations:

For improved efficiency, especially when dealing with large arrays, the function can be optimized by avoiding array merging. Instead, it can store results from recursive calls in a temporary array:

function search_optimized($array, $key, $value)
{
    $results = [];
    search_r($array, $key, $value, $results);
    return $results;
}

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

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

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

By passing the results array by reference, the function can build the final result efficiently.

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