


Tips for learning PHP arrays: Use array functions to sort arrays in descending order!
In the previous article "How to learn PHP arrays, use array functions to sort arrays in ascending order! ", we introduced the use of array functions sort(), asort(), ksort() to sort arrays in ascending order. Since there is ascending order, there is also descending order. So how to use the array function to sort the array in descending order? Let’s learn together below!
Similar to ascending sorting of arrays, there are three functions available for descending sorting of arrays, namely rsort(), arsort(), and krsort(). Let's first take a brief look at these three functions, and then use code examples to see how these array sorting functions perform descending sorting.
Three functions for sorting arrays in descending order:
rsort(): Sort array elements in descending order
- ##arsort( ): Sort the array in descending order according to the key value of the associative array
- krsort(): Sort the array in descending order according to the key name of the associative array
1. Use the rsort() function
rsort() function is used to sort the array elements in descending order, that is, from large to small and from high to low. Let’s take a look at the code example:<?php header("Content-type:text/html;charset=utf-8"); $arr = array(2, 1, 5, 16, 29, 15); rsort($arr); var_dump($arr); ?>Output result:
rsort() function has two parameters: $array (required) and $sortingtype (can be omitted). The $sortingtype parameter is used to indicate the sorting mode. For specific values, please refer to theOutput result:sort() function in the previous article. Below, arsort() and krsort() also refer to the sort() function.
<?php header("Content-type:text/html;charset=utf-8"); $arr = array(2, 1, 5, 16, 29, 15); rsort($arr,2); var_dump($arr); ?>
2. Use the arsort() function
The arsort() function will sort the associative array in descending order according to the key values and will not modify the key names in the original array. .<?php header("Content-type:text/html;charset=utf-8"); $age = array("张三"=>30,"李四"=>23,"王五"=>15,"李华"=>12,"娜娜"=>26,"小红"=>16); arsort($age); var_dump($age); arsort($age,2); var_dump($age); ?>Output result:
3. Use krsort() function
krsort() function will be based on The key names of the associative array are sorted in descending order, and the key names in the original array will not be modified.<?php header("Content-type:text/html;charset=utf-8"); $arr= array("l"=>"lemon", "o"=>"orange", "b"=>"banana", "a"=>"apple"); krsort($arr); var_dump($arr); krsort($arr,1); var_dump($arr); ?>Output result:
PHP function array array function video explanation, come and learn!
The above is the detailed content of Tips for learning PHP arrays: Use array functions to sort arrays in descending order!. For more information, please follow other related articles on the PHP Chinese website!

PHPsessionstrackuserdataacrossmultiplepagerequestsusingauniqueIDstoredinacookie.Here'showtomanagethemeffectively:1)Startasessionwithsession_start()andstoredatain$_SESSION.2)RegeneratethesessionIDafterloginwithsession_regenerate_id(true)topreventsessi

In PHP, iterating through session data can be achieved through the following steps: 1. Start the session using session_start(). 2. Iterate through foreach loop through all key-value pairs in the $_SESSION array. 3. When processing complex data structures, use is_array() or is_object() functions and use print_r() to output detailed information. 4. When optimizing traversal, paging can be used to avoid processing large amounts of data at one time. This will help you manage and use PHP session data more efficiently in your actual project.

The session realizes user authentication through the server-side state management mechanism. 1) Session creation and generation of unique IDs, 2) IDs are passed through cookies, 3) Server stores and accesses session data through IDs, 4) User authentication and status management are realized, improving application security and user experience.

Tostoreauser'snameinaPHPsession,startthesessionwithsession_start(),thenassignthenameto$_SESSION['username'].1)Usesession_start()toinitializethesession.2)Assigntheuser'snameto$_SESSION['username'].Thisallowsyoutoaccessthenameacrossmultiplepages,enhanc

Reasons for PHPSession failure include configuration errors, cookie issues, and session expiration. 1. Configuration error: Check and set the correct session.save_path. 2.Cookie problem: Make sure the cookie is set correctly. 3.Session expires: Adjust session.gc_maxlifetime value to extend session time.

Methods to debug session problems in PHP include: 1. Check whether the session is started correctly; 2. Verify the delivery of the session ID; 3. Check the storage and reading of session data; 4. Check the server configuration. By outputting session ID and data, viewing session file content, etc., you can effectively diagnose and solve session-related problems.

Multiple calls to session_start() will result in warning messages and possible data overwrites. 1) PHP will issue a warning, prompting that the session has been started. 2) It may cause unexpected overwriting of session data. 3) Use session_status() to check the session status to avoid repeated calls.

Configuring the session lifecycle in PHP can be achieved by setting session.gc_maxlifetime and session.cookie_lifetime. 1) session.gc_maxlifetime controls the survival time of server-side session data, 2) session.cookie_lifetime controls the life cycle of client cookies. When set to 0, the cookie expires when the browser is closed.


Hot AI Tools

Undresser.AI Undress
AI-powered app for creating realistic nude photos

AI Clothes Remover
Online AI tool for removing clothes from photos.

Undress AI Tool
Undress images for free

Clothoff.io
AI clothes remover

Video Face Swap
Swap faces in any video effortlessly with our completely free AI face swap tool!

Hot Article

Hot Tools

SublimeText3 English version
Recommended: Win version, supports code prompts!

VSCode Windows 64-bit Download
A free and powerful IDE editor launched by Microsoft

PhpStorm Mac version
The latest (2018.2.1) professional PHP integrated development tool

WebStorm Mac version
Useful JavaScript development tools

Dreamweaver CS6
Visual web development tools
