This section introduces PHP arrays to you. Arrays are very important in PHP programming and are used in many places. It is recommended that you master them well.
1. Array definition: <?php $arr[0] =1; $arr[1] ="hello"; $arr[3] =2.5; [0]: represents the subscript of the array, or is called a keyword $arr[0]: represents an element of the array $arr[0] =1: 1 represents the value of the array $arr: represents the name of the array Example 1, <?php /** * 定义数组 * site bbs.it-home.org */ $arr[0] =1; $arr[1] ="hello"; $arr[2] =2.5; $arr[3] =true; $arr[4] =null; //即使放入一个空,也要占用一个空间 echo '总共有'.count($arr).'个数组元素<br/>'; //函数count 计算出有多少个元素 //遍历数组 for($i =0;$i<count($arr);$i++){ echo '第'.($i+1)."个是".$arr[$i].'<br/>'; } ?> Example 2, <?php /** * 数组遍历 */ $arr["logo"] = "北京"; $arr["pwm"] = 123; $arr[123] ="abc"; //遍历 /* for($i=0;$i<count($arr);$i++){ echo $arr[$i]; }*/ //foreach遍历适用范围更广 //by bbs.it-home.org foreach($arr as $key=>$val){ echo $key.'='.$val.'<br/>'; } Results: logo=Beijing pwm=123 123=abc Note: 1. //************Special instructions <?php $arr = array(5=>"logo",45,70,); //没有给数组定义下表,PHP就会自动用前面最大的数作为第一个下标,后面的元素下标自动加1 //访问logo这个数组的值我们可以这样写 //$arr[5] = "yes"; 会替换元素的值 echo $arr[5].'<br />'; echo $arr[7]; //by bbs.it-home.org 2. //Use decimal as key, and the PHP system automatically truncates the decimal part <?php $a = array('abc'=>12,'ppp'=>234,12.7=>"world"); print_r($a); Result: Array ([abc] => 12 [ppp] => 234 [12] => world ) 3. Use true false null as keyword (subscript) <?php //使用true false null 作为关键字(下标) $a[true] ="what"; //等价于$a[1] $a[false] ="hahaa"; //等价于$a[0] $a[null] ="中国"; //等价于$a[null] 或者$a[""] //这样输出 echo $a[0].'<br/>'; echo $a[null].'<br/>'; $a[22.6]=133; //使用小数作为key,PHP系统自动截断小数部分 //用print_r来输出数组来显示数组的情况 print_r($a); echo '<br/>'; //用var_dump更详细显示数组的信息 var_dump($a); Effect: hahaa China Array ( [1] => what [0] => hahaa [] => China [22] => 133 ) array(4) { [1]=> string(4) "what" [0]=> string(5) "hahaa" [""]=> string(6) "China" [22]=> int(133 ) } 4. PHP arrays can dynamically and automatically grow <?php //PHP数组可以动态自动增长 $a = array(3,4); $a[3] =4; //echo $a[2]; //引用的数组(数组元素)不存在,系统就会报错 print_r($a); 5. Several important functions in arrays <?php $a=array(1,2,3,"one","two","three"); echo count($a).'<br/>'; //统计函数的元素个数 echo is_array($a).'<br/>'; //判断是否是一个数组 print_r($a); echo '<br/>'; var_dump($a); //显示数组信息 $b="1 2 3 'one' 'two' 'three'"; echo '<br/>-------------------------'; print_r(explode(" ",$b)); $b =array(); echo count($b); ?> Thank you for paying attention to the PHP introductory tutorials. This series of PHP basic tutorials will help PHP newbies quickly master the PHP programming language. Programmer's Home will continue to launch PHP-related tutorials for everyone, and I wish you all the best in your learning and progress! |

PHP is used to build dynamic websites, and its core functions include: 1. Generate dynamic content and generate web pages in real time by connecting with the database; 2. Process user interaction and form submissions, verify inputs and respond to operations; 3. Manage sessions and user authentication to provide a personalized experience; 4. Optimize performance and follow best practices to improve website efficiency and security.

PHP uses MySQLi and PDO extensions to interact in database operations and server-side logic processing, and processes server-side logic through functions such as session management. 1) Use MySQLi or PDO to connect to the database and execute SQL queries. 2) Handle HTTP requests and user status through session management and other functions. 3) Use transactions to ensure the atomicity of database operations. 4) Prevent SQL injection, use exception handling and closing connections for debugging. 5) Optimize performance through indexing and cache, write highly readable code and perform error handling.

Using preprocessing statements and PDO in PHP can effectively prevent SQL injection attacks. 1) Use PDO to connect to the database and set the error mode. 2) Create preprocessing statements through the prepare method and pass data using placeholders and execute methods. 3) Process query results and ensure the security and performance of the code.

PHP and Python have their own advantages and disadvantages, and the choice depends on project needs and personal preferences. 1.PHP is suitable for rapid development and maintenance of large-scale web applications. 2. Python dominates the field of data science and machine learning.

PHP is widely used in e-commerce, content management systems and API development. 1) E-commerce: used for shopping cart function and payment processing. 2) Content management system: used for dynamic content generation and user management. 3) API development: used for RESTful API development and API security. Through performance optimization and best practices, the efficiency and maintainability of PHP applications are improved.

PHP makes it easy to create interactive web content. 1) Dynamically generate content by embedding HTML and display it in real time based on user input or database data. 2) Process form submission and generate dynamic output to ensure that htmlspecialchars is used to prevent XSS. 3) Use MySQL to create a user registration system, and use password_hash and preprocessing statements to enhance security. Mastering these techniques will improve the efficiency of web development.

PHP and Python each have their own advantages, and choose according to project requirements. 1.PHP is suitable for web development, especially for rapid development and maintenance of websites. 2. Python is suitable for data science, machine learning and artificial intelligence, with concise syntax and suitable for beginners.

PHP is still dynamic and still occupies an important position in the field of modern programming. 1) PHP's simplicity and powerful community support make it widely used in web development; 2) Its flexibility and stability make it outstanding in handling web forms, database operations and file processing; 3) PHP is constantly evolving and optimizing, suitable for beginners and experienced developers.


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

AI Hentai Generator
Generate AI Hentai for free.

Hot Article

Hot Tools

SublimeText3 Chinese version
Chinese version, very easy to use

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.

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

WebStorm Mac version
Useful JavaScript development tools

ZendStudio 13.5.1 Mac
Powerful PHP integrated development environment