


PHP classic interview questions design patterns (frequently encountered), php design patterns_PHP tutorial
PHP classic interview questions design patterns (frequently encountered), PHP design patterns
Design patterns are often mentioned during the interview process, and sometimes we are asked to give examples. Application scenarios of various design patterns.
Using design patterns can reduce our workload and optimize our code.
There are many design patterns. Here we introduce 4 modes: singleton mode, factory mode, combination mode and strategy mode
If there are any problems with the code or a better way, please let me know, thank you!!!!!
/** * 单例模式 * @author YangYang <1812271619@qq.com> * 可以想成在一次http请求中只产生该类的一个对象(即只new classname一次) * 经典的例子是数据库连接(redis,mongodb,memcache等) * 在一次http请求中我们可能需要对数据库做增删改查多条sql操作 * 但是如果一次http请求中每执行一条sql我们就mysql_connect(),很明显会导致服务器资源的浪费 * 为了节约资源,就可以通过单例模式来实现一次http请求只做一次mysql_connect() * 即将mysql_connect()放在类方法的__construct中,并将__construct方法做成私有, * 这样只能通过getInstance()方法来获得mysql_connect()的资源连接符 * getInstance()方法中判断是否已经存在myql连接符,如果存在就直接返回该连接符 * 否则new classname()即调用了__construct方法执行了mysql_connect()得到了资源连接符,并返回连接符 * 因为现在PHP已不再建议直接使用mysql函数进行数据库操作,而是建议通过PDO进行数据库操作,所以这里写一个简易PDO连接的单例模式 * 这里只是讲解单例原理,数据库的防sql注入等问题不做考虑 * 准备工作 数据库:test 数据表:user 字段:id name 记录:1 CodeAnti * 最终运行结果: 数据表user中id=1这条记录被删除 */ class SinglePDO { private static $_instance = null; private $_pdo; //私有,防止外部直接实例化new SinglePDO(...) private function __construct($dsn,$dbUser,$dbPassword) { try{ $this->_pdo = new PDO($dsn,$dbUser,$dbPassword); $this->_pdo->exec('set names utf8'); }catch(PDOException $e){ die("Error:{$e->getMessage()}"); } } //私有,防止克隆 private function __clone(){} //获取连接实例 public static function getInstance($dsn,$dbUser,$dbPassword) { if(self::$_instance === null) self::$_instance = new self($dsn,$dbUser,$dbPassword); return self::$_instance; } //执行sql public function execSql($sql) { $result = $this->_pdo->exec($sql); return $result; } } $dsn = "mysql:host=localhost;dbname=test"; $dbUser = "root"; $dbPassword = ""; $sql = "delete from user where id = 1"; $pdo = SinglePDO::getInstance($dsn,$dbUser,$dbPassword); $result = $pdo->execSql($sql); //$pdo->execSql($sql)多次调用,但仍然是同一个pdo对象 print_r($result);

What’s still popular is the ease of use, flexibility and a strong ecosystem. 1) Ease of use and simple syntax make it the first choice for beginners. 2) Closely integrated with web development, excellent interaction with HTTP requests and database. 3) The huge ecosystem provides a wealth of tools and libraries. 4) Active community and open source nature adapts them to new needs and technology trends.

PHP and Python are both high-level programming languages that are widely used in web development, data processing and automation tasks. 1.PHP is often used to build dynamic websites and content management systems, while Python is often used to build web frameworks and data science. 2.PHP uses echo to output content, Python uses print. 3. Both support object-oriented programming, but the syntax and keywords are different. 4. PHP supports weak type conversion, while Python is more stringent. 5. PHP performance optimization includes using OPcache and asynchronous programming, while Python uses cProfile and asynchronous programming.

PHP is mainly procedural programming, but also supports object-oriented programming (OOP); Python supports a variety of paradigms, including OOP, functional and procedural programming. PHP is suitable for web development, and Python is suitable for a variety of applications such as data analysis and machine learning.

PHP originated in 1994 and was developed by RasmusLerdorf. It was originally used to track website visitors and gradually evolved into a server-side scripting language and was widely used in web development. Python was developed by Guidovan Rossum in the late 1980s and was first released in 1991. It emphasizes code readability and simplicity, and is suitable for scientific computing, data analysis and other fields.

PHP is suitable for web development and rapid prototyping, and Python is suitable for data science and machine learning. 1.PHP is used for dynamic web development, with simple syntax and suitable for rapid development. 2. Python has concise syntax, is suitable for multiple fields, and has a strong library ecosystem.

PHP remains important in the modernization process because it supports a large number of websites and applications and adapts to development needs through frameworks. 1.PHP7 improves performance and introduces new features. 2. Modern frameworks such as Laravel, Symfony and CodeIgniter simplify development and improve code quality. 3. Performance optimization and best practices further improve application efficiency.

PHPhassignificantlyimpactedwebdevelopmentandextendsbeyondit.1)ItpowersmajorplatformslikeWordPressandexcelsindatabaseinteractions.2)PHP'sadaptabilityallowsittoscaleforlargeapplicationsusingframeworkslikeLaravel.3)Beyondweb,PHPisusedincommand-linescrip

PHP type prompts to improve code quality and readability. 1) Scalar type tips: Since PHP7.0, basic data types are allowed to be specified in function parameters, such as int, float, etc. 2) Return type prompt: Ensure the consistency of the function return value type. 3) Union type prompt: Since PHP8.0, multiple types are allowed to be specified in function parameters or return values. 4) Nullable type prompt: Allows to include null values and handle functions that may return null values.


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