深入了解PHP：从入门到精通

变量声明和输出

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

条件语句

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

循环语句

for ($i = 0; $i < 5; $i++) { echo $i; }登录后复制

函数的定义和调用

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

数组的声明和遍历

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

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!登录后复制

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()); }登录后复制

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."; }登录后复制

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); }登录后复制

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();登录后复制

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();登录后复制

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."; }登录后复制

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); }登录后复制

$sql = "SELECT * FROM users WHERE username = '$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."; }登录后复制