Let's talk about commonly used sorting methods (algorithms) in PHP

As an important programming language, PHP actually performs well in many aspects. In data processing, sorting algorithms are the most common and important part. PHP provides a variety of sorting algorithms. The following is a detailed introduction to the commonly used sorting methods in PHP.

1. Bubble sort

Bubble sort is one of the most classic sorting algorithms in PHP. This algorithm completes sorting by traversing and comparing the sizes of two adjacent elements, and then continuously exchanging the order. This method can be implemented using a for loop or while loop.

<?php function bubble_sort($arr){
    $length = count($arr);
    for($i=0;$i<$length;$i++){
        for($j=$i+1;$j<$length;$j++){
            if($arr[$i]>$arr[$j]){
                $tmp = $arr[$i];
                $arr[$i] = $arr[$j];
                $arr[$j] = $tmp;
            }
        }
    }
    return $arr;
}

2. Quick Sort

Quick sort is one of the fastest sorting algorithms in PHP. This algorithm uses a recursive method to split the array into two parts, using one pivot element at a time to split the array into smaller and larger subarrays. Afterwards, the sub-arrays are continuously sorted recursively, and finally the sorted array is obtained.

There are many ways to implement quick sort in PHP, such as recursive and non-recursive methods.

<?php function quick_sort($arr){
    $length = count($arr);
    if($length<=1){
        return $arr;
    }
    $left_array = array();
    $right_array = array();
    $middle = $arr[0];
    for($i=1;$i<$length;$i++){
        if($arr[$i]<$middle){
            $left_array[] = $arr[$i];
        }else{
            $right_array[] = $arr[$i];
        }
    }
    $left_array = quick_sort($left_array);
    $right_array = quick_sort($right_array);
    return array_merge($left_array, array($middle), $right_array);
}

3. Selection sort

Selection sort is another classic sorting algorithm in PHP. This algorithm works by finding the smallest element in an array and placing it at the front of the array, then doing the same for the remaining elements. The time complexity of this algorithm is O(n²).

<?php function select_sort($arr){
    $length = count($arr);
    for($i=0;$i<$length;$i++){
        $min = $i;
        for($j=$i+1;$j<$length;$j++){
            if($arr[$j]<$arr[$min]){
                $min = $j;
            }
        }
        if($min!=$i){
            $tmp = $arr[$i];
            $arr[$i] = $arr[$min];
            $arr[$min] = $tmp;
        }
    }
    return $arr;
}

4. Insertion sort

Insertion sort is another simple sorting algorithm in PHP. This algorithm compares the size and position of the current element with the previously sorted element, and then inserts the element into the appropriate position. The time complexity of this algorithm is O(n²).

<?php function insert_sort($arr){
    $length = count($arr);
    for($i=1;$i<$length;$i++){
        $tmp = $arr[$i];
        $j = $i-1;
        while($j>=0 && $arr[$j]>$tmp){
            $arr[$j+1] = $arr[$j];
            $j--;
        }
        $arr[$j+1] = $tmp;
    }
    return $arr;
}

Summary:

The above four sorting methods are common sorting algorithms in PHP. In practical applications, selection sort and insertion sort are generally used for sorting a small amount of data, bubble sort is more commonly used when the data size is small, and quick sort is the most commonly used sorting algorithm when the data size is large. Developers can choose an appropriate sorting algorithm based on the actual situation.

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