PHP multidimensional array sorting performance optimization: from code to algorithm

PHP multi-dimensional array sorting performance optimization can be improved through both code and algorithm. Code optimization includes using usort and self-written comparison functions to avoid excessive comparisons and copies. Algorithm optimization involves quick sort and merge sort algorithms. Quick sort is suitable for large arrays, while merge sort is suitable for any type of data. The code example shows how to sort an array with child elements using these two algorithms, quick sort by id and merge sort by name.

PHP Multidimensional Array Sorting Performance Optimization: Code and Algorithm

Introduction

Multidimensional arrays are a common data structure in PHP and are very useful when dealing with complex data. However, performance issues arise when you need to sort multidimensional arrays. This article will explore the performance optimization of multi-dimensional array sorting in PHP and provide solutions from both code and algorithm aspects.

Code optimization

Use usort and self-written comparison function

Compared to the built-in sort function, the usort function provides greater flexibility as it allows you to use a custom comparison function to sort array elements. Self-written comparison functions can be customized for your specific sorting needs, making sorting more efficient.

<?php
function compare($a, $b) {
  return $a['key'] <=> $b['key'];
}

usort($array, 'compare');

Avoid excessive comparison and copying

During the sorting process, array elements will be compared and copied repeatedly. Performance can be improved by reducing the number of unnecessary comparisons and copies. The following tips can help you avoid these operations:

• Use merge sort: Merge sort is a divide-and-conquer algorithm that can reduce the number of unnecessary comparisons.
• Create a copy to sort: Sort a copy of the array to avoid modifying the original array.

Algorithm optimization

Use quick sort:

Quick sort is an efficient sorting algorithm, especially Suitable for large arrays. It works by dividing the array into smaller parts and sorting the parts recursively.

<?php
function quickSort($array) {
  if (count($array) <= 1) {
    return $array;
  }
  $pivot = $array[0];
  $left = array_filter($array, function ($item) use ($pivot) {
    return $item < $pivot;
  });
  $right = array_filter($array, function ($item) use ($pivot) {
    return $item >= $pivot;
  });
  return array_merge(quickSort($left), [$pivot], quickSort($right));
}

Use merge sort:

Merge sort is also an efficient sorting algorithm and is suitable for any type of data. It works by recursively dividing the array into smaller parts, sorting the parts, and then merging them.

<?php
function mergeSort($array) {
  if (count($array) <= 1) {
    return $array;
  }
  $mid = intdiv(count($array), 2);
  $left = mergeSort(array_slice($array, 0, $mid));
  $right = mergeSort(array_slice($array, $mid));
  return merge($left, $right);
}

function merge($left, $right) {
  $result = [];
  while (count($left) > 0 && count($right) > 0) {
    if ($left[0] <= $right[0]) {
      $result[] = array_shift($left);
    } else {
      $result[] = array_shift($right);
    }
  }
  return array_merge($result, $left, $right);
}

Practical case

The following is a practical case that shows how to use quick sort and merge sort to sort a multi-dimensional array with sub-elements:

<?php
$array = [
  ['id' => 1, 'name' => 'John'],
  ['id' => 3, 'name' => 'Alice'],
  ['id' => 2, 'name' => 'Bob']
];

// 使用快速排序按 id 排序
$quickSortedArray = quickSort($array);

// 使用归并排序按 name 排序
$mergeSortedArray = mergeSort($array);

// 输出排序后的数组
print_r($quickSortedArray);
print_r($mergeSortedArray);

Output:

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

    [1] => Array
        (
            [id] => 2
            [name] => Bob
        )

    [2] => Array
        (
            [id] => 3
            [name] => Alice
        )

)

Array
(
    [0] => Array
        (
            [id] => 2
            [name] => Bob
        )

    [1] => Array
        (
            [id] => 1
            [name] => John
        )

    [2] => Array
        (
            [id] => 3
            [name] => Alice
        )

)

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