Can you Preserve Key Order While Sorting Associative Arrays in PHP?-PHP Tutorial-php.cn

Can you Preserve Key Order While Sorting Associative Arrays in PHP?

Susan Sarandon

Release： 2024-11-02 20:12:31

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Can you Preserve Key Order While Sorting Associative Arrays in PHP?

Preserving Key Order During Sorting with PHP's uasort

Query:

Is it possible to sort the values of an associative array in PHP while maintaining the original order of keys, using PHP's built-in sorting functions?

Challenge:

To achieve a stable sort where equal values retain their initial key order, a custom sorting function must be employed since PHP does not support stable sorting natively.

Solution:

A custom merge sort, which guarantees O(n*log(n)) complexity and maintains stability, can be used:

<code class="php">function mergesort(&$array, $cmp_function = 'strcmp') {
    // Handle base cases
    if (count($array) < 2) return;
    
    // Split the array into halves
    $halfway = count($array) / 2;
    $array1 = array_slice($array, 0, $halfway);
    $array2 = array_slice($array, $halfway);
    
    // Recursively sort the halves
    mergesort($array1, $cmp_function);
    mergesort($array2, $cmp_function);
    
    // Merge the sorted halves
    $array = array();
    $ptr1 = $ptr2 = 0;

    while ($ptr1 < count($array1) && $ptr2 < count($array2)) {
        if (call_user_func($cmp_function, $array1[$ptr1], $array2[$ptr2]) < 1) {
            $array[] = $array1[$ptr1++];
        } else {
            $array[] = $array2[$ptr2++];
        }
    }
    
    // Merge the remaining elements
    while ($ptr1 < count($array1)) $array[] = $array1[$ptr1++];
    while ($ptr2 < count($array2)) $array[] = $array2[$ptr2++];
}</code>

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Alternative Resource:

An informative forum thread can be found at this link: [Forum Thread Link]

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