php does not use function array sorting

PHP is a popular programming language used for web development. It has powerful functions and a rich function library, and various tasks can be completed by using these functions. One of them is sorting an array. PHP provides several functions, such as sort(), asort() and ksort(), etc., which can sort array elements. But what if you don't want to use a function and want to sort the array manually? In this article, we will discuss how to sort array using PHP without using functions.

First of all, we need to understand that the basic principle of sorting is comparison and exchange. We can understand this process by writing a basic sorting algorithm. The following is an example of using the Bubble Sort algorithm.

<?php
// PHP不使用函数的数组排序
$numbers = array(4, 3, 8, 1);

$length = count($numbers);
for($i = 0; $i < $length; $i++) {
    for($j = 0; $j < $length-1; $j++) {
        if($numbers[$j] > $numbers[$j+1]) {
            $temp = $numbers[$j];
            $numbers[$j] = $numbers[$j+1];
            $numbers[$j+1] = $temp;
        }
    }
}

// 输出结果
foreach($numbers as $number) {
    echo $number . " ";
}
?>

In this example, we use a double loop to compare each element in the array. If the current element is larger than the next element, we swap their positions. In this way we end up with an array sorted in ascending order.

Of course, this algorithm is just an example, you can write your own sorting algorithm to achieve specific sorting purposes. However, no matter which algorithm you use, the basic principle is the same: compare and exchange.

In addition to this, we can also use another method to sort the array, called "selection sort". This algorithm works by scanning the array and selecting the smallest element on each iteration. Below is an example of sorting an array using the selection sort algorithm.

<?php
// PHP不使用函数的数组排序
$numbers = array(4, 3, 8, 1);

$length = count($numbers);

for ($i = 0; $i < $length; $i++) {
    // 选取$i位置后的最小值
    $min = $i;
    for ($j = $i + 1; $j < $length; $j++) {
        if ($numbers[$j] < $numbers[$min]) {
            $min = $j;
        }
    }
    // 如果选取的不是当前位置，则交换位置
    if ($min !== $i) {
        $temp = $numbers[$i];
        $numbers[$i] = $numbers[$min];
        $numbers[$min] = $temp;
    }
}

// 输出结果
foreach ($numbers as $number) {
    echo $number . " ";
}
?>

In this example, we implement the selection sort algorithm through a double loop. The outer loop is used to scan the array, and the inner loop is used to find the minimum value. Once the inner loop completes, we place the found minimum value at the current position and continue with the next iteration.

Using this example, you can start using your own algorithm to sort arrays without having to use PHP's built-in functions. This is a very basic, but useful skill that can help you gain a deeper understanding of PHP as well as other programming languages.

In short, PHP provides many built-in functions to help us complete various tasks, including sorting arrays. However, in some cases you may need to manually write an algorithm to accomplish this task, such as in some applications with high performance requirements. Using the basic principles introduced in this article, you can write your own sorting algorithm to meet your specific needs.

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