How to sort by not in an array using PHP

In the process of PHP development, we often need to sort arrays. Normally, we use the built-in sort() function to implement sorting. However, if you want to sort by elements that are not in the array, you need to use some special techniques to achieve it. This article will explain how to sort by not in an array using PHP.

1. Principle

When we need to sort by elements that are not in the array, we first need to add the elements that are not in the array to the array. It can be added to the end of the array or added to the array in a certain order. Next, we need to sort the array. Finally, just delete the elements that are not in the array from the array.

2. Sample code

The following is a sample code that demonstrates how to sort by elements that are not in the array:

<?php
//不在数组中的元素
$not_in_array = array(&#39;a&#39;, &#39;c&#39;, &#39;e&#39;);

//待排序数组
$array = array(&#39;d&#39;, &#39;b&#39;, &#39;f&#39;);

//将不在数组中的元素加入到数组中
foreach ($not_in_array as $value) {
    array_push($array, $value);
}

//排序
sort($array);

//删除不在数组中的元素
foreach ($not_in_array as $value) {
    unset($array[array_search($value, $array)]);
}

//输出结果
print_r($array);
?>

In the above sample code, first Defines an array of elements that are not in the array, and the array to be sorted. Then, use a foreach loop to add elements that are not in the array to the array to be sorted. Next, use the sort() function to sort the array to be sorted. Finally, use the foreach loop and the unset() function to delete elements that are not in the array from the array to be sorted, and output the result.

3. Code Description

In the above example code, we need to use several key functions and operations. Here are some details:

1. array_push(): This function is used to add one or more values ​​to the end of an array.
2. sort(): This function is used to sort the array.
3. unset(): This function is used to delete one or more variables.
4. array_search(): This function is used to search for the specified value in the array and return its key name.

In the above example code, we first add elements that are not in the array to the original array using the array_push() function, and then use the sort() function to sort the original array. Finally, we use a foreach loop and the unset() function to remove elements from the array that are not in the array.

4. Notes

When using the above method to sort, you need to pay attention to the following points:

1. Elements that are not in the array should be unique, otherwise May cause incorrect sorting results.
2. Elements not in the array should be of the same type as the elements in the original array, otherwise the sorting may fail.
3. When using the unset() function to delete elements, you should use the array_search() function to search for the key name of the element to avoid deleting elements by mistake.

5. Summary

This article introduces how to use PHP to sort by elements that are not in the array. By adding elements that are not in the array to the original array, using the sort() function to sort, and finally deleting the elements that are not in the array from the array, you can sort by the elements that are not in the array. However, during the actual development process, some details and features need to be paid attention to to avoid errors and unnecessary trouble.

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