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.";

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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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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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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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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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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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