PHP 简介

PHP（Hypertext Preprocessor）是一种开源的服务器端脚本语言，专为 Web 开发设计。它嵌入 HTML 中运行，支持动态网页生成、数据库交互和会话管理，广泛应用于 CMS（如 WordPress）、电商平台（如 Magento）和 API 开发。

PHP 基础语法

PHP 代码以<?php开头，以?>结尾。变量以$符号开头，无需声明类型：

<?php $message = "Hello, World!"; echo $message; // 输出：Hello, World! ?>

数据类型与运算符

PHP 支持多种数据类型，包括字符串、整数、浮点数、布尔值、数组和对象。常见运算符：

$a = 10; $b = 3; echo $a + $b; // 13 echo $a % $b; // 1（取模）

控制结构

条件语句和循环示例：

// if-else if ($age >= 18) { echo "Adult"; } else { echo "Minor"; } // for 循环 for ($i = 0; $i < 5; $i++) { echo $i; }

函数与数组

自定义函数和数组操作：

function add($x, $y) { return $x + $y; } echo add(2, 3); // 5 // 关联数组 $user = ["name" => "Alice", "age" => 25]; echo $user["name"]; // Alice

数据库连接（MySQL）

使用 PDO（PHP Data Objects）连接数据库：

$dsn = "mysql:host=localhost;dbname=test"; $user = "root"; $pass = ""; try { $pdo = new PDO($dsn, $user, $pass); echo "Connected successfully"; } catch (PDOException $e) { echo "Connection failed: " . $e->getMessage(); }

文件操作

读写文件示例：

// 写入文件 file_put_contents("test.txt", "Hello PHP"); // 读取文件 echo file_get_contents("test.txt"); // Hello PHP

面向对象编程（OOP）

类与对象的基本用法：

class Car { public $color; public function start() { echo "Engine started!"; } } $myCar = new Car(); $myCar->color = "red"; $myCar->start(); // Engine started!

错误处理

使用try-catch捕获异常：

try { $result = 10 / 0; } catch (DivisionByZeroError $e) { echo "Error: " . $e->getMessage(); }

常用框架与工具

• Laravel：全栈框架，提供路由、ORM 和模板引擎。
• Symfony：模块化框架，适合大型项目。
• Composer：PHP 依赖管理工具。

安装 Laravel 示例（通过 Composer）：

composer create-project laravel/laravel my-project

安全性建议

• 使用预处理语句防止 SQL 注入。
• 过滤用户输入（如htmlspecialchars()）。
• 避免暴露敏感信息（如数据库密码）。

PHP 的灵活性和丰富的生态系统使其成为 Web 开发的重要工具，适合从简单脚本到复杂企业级应用。

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