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

Searching for Key-Value Pairs in Multidimensional PHP Arrays

Multidimensional arrays in PHP can be challenging to navigate, especially when searching for specific key-value pairs. This comprehensive guide presents an efficient method for quickly retrieving all subarrays containing a specified key-value pair, irrespective of the array's nesting depth.

The proposed solution is a recursive function named search, which takes an array, a key, and a value as parameters. It checks if the key-value pair exists at the current level of the array and, if so, adds the current subarray to the results. Subsequently, it iterates over each subarray, calling itself recursively to expand the search to deeper levels.

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

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

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

    return $results;
}

By employing recursion, the search function explores the entire array structure, ensuring that all matching key-value pairs are identified.

For instance, 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"));

And searching for key=name and value="cat 1", the function will return:

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

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

)

To enhance efficiency, an alternate implementation merges the results of recursive calls into a single $results array instead of creating separate arrays:

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

Note that the ampersand & in the parameter list indicates pass-by-reference, ensuring that all recursive calls modify the same $results array.

This robust and versatile solution empowers developers to seamlessly search for key-value pairs in multidimensional PHP arrays, regardless of their depth or complexity.

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