深入了解PHP：从入门到精通-php教程-PHP中文网

深入了解PHP：从入门到精通

引言：
PHP是一种广泛应用于web开发的服务器端脚本语言，它简单易学，适用于初学者，也提供了丰富的功能和扩展性，能够满足复杂的开发需求。本文将从入门到精通，通过具体的代码示例，带您逐步了解PHP的各个方面。

一、基础知识

变量声明和输出

$name = "John"; $age = 25; echo "My name is " . $name . " and I am " . $age . " years old.";

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条件语句

$score = 90; if ($score >= 60) { echo "You passed the exam!"; } else { echo "You failed the exam."; }

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循环语句
```
for ($i = 0; $i < 5; $i++) { echo $i; }
```
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函数的定义和调用

function sayHello($name) { echo "Hello, " . $name . "!"; } sayHello("Tom");

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二、数组和字符串

数组的声明和遍历

$fruits = ["apple", "banana", "orange"]; foreach ($fruits as $fruit) { echo $fruit; }

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字符串操作

$str = "Hello, PHP!"; echo strlen($str); // 输出：12 echo strtoupper($str); // 输出：HELLO, PHP! echo substr($str, 7); // 输出：PHP!

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三、数据库操作

连接数据库

$servername = "localhost"; $username = "root"; $password = "123456"; $dbname = "myDB"; $conn = mysqli_connect($servername, $username, $password, $dbname); if (!$conn) { die("Connection failed: " . mysqli_connect_error()); }

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查询数据

$sql = "SELECT * FROM users"; $result = mysqli_query($conn, $sql); if (mysqli_num_rows($result) > 0) { while ($row = mysqli_fetch_assoc($result)) { echo "Name: " . $row['name'] . ", Age: " . $row['age']; } } else { echo "No results found."; }

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插入数据

$sql = "INSERT INTO users (name, age) VALUES ('John', 25)"; if (mysqli_query($conn, $sql)) { echo "Data inserted successfully."; } else { echo "Error: " . mysqli_error($conn); }

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四、面向对象编程

类的定义和实例化

class Car { public $color; public function drive() { echo "Driving..."; } } $car = new Car(); $car->color = "red"; $car->drive();

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继承和多态

class SportsCar extends Car { public function drive() { echo "Driving at high speed!"; } } $sportsCar = new SportsCar(); $sportsCar->color = "blue"; $sportsCar->drive();

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五、常见应用

文件上传

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$targetDir = "uploads/"; $targetFile = $targetDir . basename($_FILES["file"]["name"]); if (move_uploaded_file($_FILES["file"]["tmp_name"], $targetFile)) { echo "File uploaded successfully."; } else { echo "Error uploading file."; }

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用户注册与登录

$hashedPassword = password_hash($password, PASSWORD_DEFAULT); $sql = "INSERT INTO users (username, password) VALUES ('$username', '$hashedPassword')"; if (mysqli_query($conn, $sql)) { echo "Registration successful. You can now login."; } else { echo "Error: " . mysqli_error($conn); }

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$sql = "SELECT * FROM users WHERE username = '$username'"; $result = mysqli_query($conn, $sql); if (mysqli_num_rows($result) > 0) { $row = mysqli_fetch_assoc($result); if (password_verify($password, $row['password'])) { echo "Login successful."; } else { echo "Password incorrect."; } } else { echo "Username not found."; }

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结语：
通过本文的介绍和实例代码，希望读者能够从PHP的基础知识开始，逐步深入了解PHP的各个方面，从而掌握PHP的高级应用技巧，提升自己的开发能力。同时，也欢迎读者在实践中探索更多有趣和创新的PHP应用。

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