search
HomeBackend DevelopmentPHP TutorialIntroduction to the usage of PHP array_flip() function

PHP language is a widely used Web programming language. Arrays are a very commonly used data structure during the development of Web applications. The key-value pairs in the array allow programmers to organize and manage data conveniently. PHP's array_flip() function is a very useful function. It can exchange the keys and values ​​of the array, using the original keys as values ​​and the original values ​​as keys. This article will introduce you to the usage of PHP's array_flip() function and its application in actual programming.

  1. Basic usage of array_flip() function

The array_flip() function in PHP can exchange the keys and values ​​​​of an array, that is, the original keys become Values, which were originally values, become keys. Its syntax format is as follows:

array array_flip ( array $array )

Parameter description:

  • array: Array that needs to be exchanged for key/value pairs

Return value: Return A new array in which the keys of the original array become the values ​​of the new array and the values ​​of the original array become the keys of the new array.

The following is an example of using the array_flip() function:

$old_array = array("apple"=>"fruit", "carrot"=>"vegetable");
$new_array = array_flip($old_array);
var_dump($new_array);

In this example, the old array $old_array contains 2 elements, namely "apple" and "carrot". Their values ​​are "fruit" and "vegetable" respectively. This array uses the form of an associative array. After calling the array_flip() function, it will return a new array $new_array. In $new_array, "fruit" and "vegetable" become the keys of the new array, and "apple" and "carrot" become the values ​​of the new array. Finally, we use the var_dump() function to output the new array. The output result is as follows:

array(2) {
  ["fruit"]=>
  string(5) "apple"
  ["vegetable"]=>
  string(6) "carrot"
}

2. Using the array_flip() function in programming

The use of the array_flip() function is very simple, but in practice It may be used frequently in programming.

This section will introduce some example uses of the array_flip() function in programming.

2.1 Usage 1: Delete duplicate items in the array

Elements in the array may be duplicated. If you need to delete duplicate elements in an array, you can first use the array_flip() function to exchange the key-value pairs of the array, so that you can use the array_unique() function to delete the duplicate keys, and finally use the array_flip() function to restore the key/value pairs. to its original form. The specific example is as follows:

$old_array = array("apple", "banana", "carrot", "apple", "grape", "banana");
$new_array = array_flip($old_array);
$new_array = array_unique($new_array);
$new_array = array_flip($new_array);
print_r($new_array);

Run this program, the output result is:

Array
(
 [0] => apple
 [1] => banana
 [2] => carrot
 [4] => grape
)

By using the array_flip() function, we first exchange the keys and values ​​of the array, and then use the array_unique() function Duplicate keys in the array are removed, and finally the keys and values ​​of the array are restored using the array_flip() function.

2.2 Usage 2: Find the value in the array

Use the array_flip() function to quickly find the key corresponding to a value in the array. If a value is unique, you can first use the array_flip() function to exchange the key and value, and then use the array_key_exists() function or isset() function to determine whether the key corresponding to this value exists. The specific example is as follows:

$old_array = array("apple"=>"fruit", "banana"=>"fruit", "carrot"=>"vegetable");
$new_array = array_flip($old_array);
if (isset($new_array["fruit"])) {
  echo "fruit is found in array";
}

The output result is:

fruit is found in array

In the above code, we exchange the keys and values ​​of the $old_array array, and then use the isset() function to find the new array Whether the value "fruit" exists in $new_array, because the array has been exchanged, so we are actually looking for the key "fruit" in the original array $old_array. Running the program, the output is "fruit is found in array".

2.3 Usage 3: Generate enumeration array

In program development, sometimes it is necessary to define a limited number of sets, such as weeks, seasons, etc. You can use the array_flip() function to use the values ​​in an array as the keys of a new array, and then use the range() function to generate a sequence of numbers in a specified range as the value of the new array. The specific example is as follows:

$old_array = array("Monday", "Tuesday", "Wednesday", "Thursday", "Friday", "Saturday", "Sunday");
$new_array = array_flip($old_array);
$enum_array = array_map(function(){static $index = 1; return $index++;}, range(1, count($old_array)));
$new_array = array_replace($new_array, $enum_array);
print_r($new_array);

The output result is:

Array
(
 [Monday] => 1
 [Tuesday] => 2
 [Wednesday] => 3
 [Thursday] => 4
 [Friday] => 5
 [Saturday] => 6
 [Sunday] => 7
)

In the above code, we first use the array_flip() function to exchange the keys and values ​​​​of the original array, and then use the range() function Generate a sequence with the length of the original array, and then use the array_map() function to replace this sequence with the value of the new array. Finally, we use the array_replace() function to merge this enumeration array with the original array of key/value pairs to form a new array with enumeration values.

The above is the detailed content of Introduction to the usage of PHP array_flip() function. For more information, please follow other related articles on the PHP Chinese website!

Statement
The content of this article is voluntarily contributed by netizens, and the copyright belongs to the original author. This site does not assume corresponding legal responsibility. If you find any content suspected of plagiarism or infringement, please contact admin@php.cn
php怎么把负数转为正整数php怎么把负数转为正整数Apr 19, 2022 pm 08:59 PM

php把负数转为正整数的方法:1、使用abs()函数将负数转为正数,使用intval()函数对正数取整,转为正整数,语法“intval(abs($number))”;2、利用“~”位运算符将负数取反加一,语法“~$number + 1”。

php怎么实现几秒后执行一个函数php怎么实现几秒后执行一个函数Apr 24, 2022 pm 01:12 PM

实现方法:1、使用“sleep(延迟秒数)”语句,可延迟执行函数若干秒;2、使用“time_nanosleep(延迟秒数,延迟纳秒数)”语句,可延迟执行函数若干秒和纳秒;3、使用“time_sleep_until(time()+7)”语句。

php怎么除以100保留两位小数php怎么除以100保留两位小数Apr 22, 2022 pm 06:23 PM

php除以100保留两位小数的方法:1、利用“/”运算符进行除法运算,语法“数值 / 100”;2、使用“number_format(除法结果, 2)”或“sprintf("%.2f",除法结果)”语句进行四舍五入的处理值,并保留两位小数。

php怎么根据年月日判断是一年的第几天php怎么根据年月日判断是一年的第几天Apr 22, 2022 pm 05:02 PM

判断方法:1、使用“strtotime("年-月-日")”语句将给定的年月日转换为时间戳格式;2、用“date("z",时间戳)+1”语句计算指定时间戳是一年的第几天。date()返回的天数是从0开始计算的,因此真实天数需要在此基础上加1。

php怎么判断有没有小数点php怎么判断有没有小数点Apr 20, 2022 pm 08:12 PM

php判断有没有小数点的方法:1、使用“strpos(数字字符串,'.')”语法,如果返回小数点在字符串中第一次出现的位置,则有小数点;2、使用“strrpos(数字字符串,'.')”语句,如果返回小数点在字符串中最后一次出现的位置,则有。

php怎么替换nbsp空格符php怎么替换nbsp空格符Apr 24, 2022 pm 02:55 PM

方法:1、用“str_replace(" ","其他字符",$str)”语句,可将nbsp符替换为其他字符;2、用“preg_replace("/(\s|\&nbsp\;||\xc2\xa0)/","其他字符",$str)”语句。

php怎么设置implode没有分隔符php怎么设置implode没有分隔符Apr 18, 2022 pm 05:39 PM

在PHP中,可以利用implode()函数的第一个参数来设置没有分隔符,该函数的第一个参数用于规定数组元素之间放置的内容,默认是空字符串,也可将第一个参数设置为空,语法为“implode(数组)”或者“implode("",数组)”。

php字符串有没有下标php字符串有没有下标Apr 24, 2022 am 11:49 AM

php字符串有下标。在PHP中,下标不仅可以应用于数组和对象,还可应用于字符串,利用字符串的下标和中括号“[]”可以访问指定索引位置的字符,并对该字符进行读写,语法“字符串名[下标值]”;字符串的下标值(索引值)只能是整数类型,起始值为0。

See all articles

Hot AI Tools

Undresser.AI Undress

Undresser.AI Undress

AI-powered app for creating realistic nude photos

AI Clothes Remover

AI Clothes Remover

Online AI tool for removing clothes from photos.

Undress AI Tool

Undress AI Tool

Undress images for free

Clothoff.io

Clothoff.io

AI clothes remover

AI Hentai Generator

AI Hentai Generator

Generate AI Hentai for free.

Hot Article

R.E.P.O. Energy Crystals Explained and What They Do (Yellow Crystal)
2 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
Repo: How To Revive Teammates
4 weeks agoBy尊渡假赌尊渡假赌尊渡假赌
Hello Kitty Island Adventure: How To Get Giant Seeds
3 weeks agoBy尊渡假赌尊渡假赌尊渡假赌

Hot Tools

SublimeText3 Chinese version

SublimeText3 Chinese version

Chinese version, very easy to use

SublimeText3 Mac version

SublimeText3 Mac version

God-level code editing software (SublimeText3)

MantisBT

MantisBT

Mantis is an easy-to-deploy web-based defect tracking tool designed to aid in product defect tracking. It requires PHP, MySQL and a web server. Check out our demo and hosting services.

Dreamweaver CS6

Dreamweaver CS6

Visual web development tools

DVWA

DVWA

Damn Vulnerable Web App (DVWA) is a PHP/MySQL web application that is very vulnerable. Its main goals are to be an aid for security professionals to test their skills and tools in a legal environment, to help web developers better understand the process of securing web applications, and to help teachers/students teach/learn in a classroom environment Web application security. The goal of DVWA is to practice some of the most common web vulnerabilities through a simple and straightforward interface, with varying degrees of difficulty. Please note that this software