PHP 基础教程

<?php
// 这是单行注释
echo "Hello, PHP!\n";
/* 这是多行注释 */
$name = "World";
echo "Hello, $name!\n";
?>

<?php
$name = "PHP";
$version = 8.3;
$isPopular = true;
$year = 2026;
echo "语言：$name\n";
echo "版本：$version\n";
var_dump($name);
var_dump($version);
var_dump($isPopular);
var_dump($year);
?>

<?php
define("SITE_NAME", "Helpme");
const MAX_USERS = 100;
echo "站点：" . SITE_NAME . "\n";
echo "最大用户数：" . MAX_USERS . "\n";
$lang = "PHP";
$msg = "正在学习" . $lang;
echo $msg . "\n";
?>

<?php
$name = "Marvis";
$text = <<<EOT
你好，$name！
这是 heredoc 多行文本。
支持变量插值与"引号"。
EOT;
echo $text;
?>

<?php
$a = 17;
$b = 5;
echo "和：" . ($a + $b) . "\n";
echo "差：" . ($a - $b) . "\n";
echo "积：" . ($a * $b) . "\n";
echo "商：" . ($a / $b) . "\n";
echo "整除：" . intdiv($a, $b) . "\n";
echo "余数：" . ($a % $b) . "\n";
echo "幂：" . ($a ** $b) . "\n";
?>

<?php
$a = 8;
$b = 12;
var_dump($a > $b);
var_dump($a !== $b);
var_dump($a < 10 && $b > 10);
var_dump(!($a === 8));
?>

<?php
$s = "42";
$n = (int)$s + 8;
$f = (float)$n;
$t = (string)$f;
echo "整数：$n，类型：" . gettype($n) . "\n";
echo "浮点：$f，类型：" . gettype($f) . "\n";
echo "字符串：$t，类型：" . gettype($t) . "\n";
?>

<?php
$config = null;
$port = $config ?? 8080;
echo "端口：" . $port . "\n";

$username = "";
$display = $username ?: "游客";
echo "显示名：" . $display . "\n";

$real = "admin";
echo "真实名：" . ($real ?: "游客") . "\n";
?>

<?php
$score = 85;
if ($score >= 90) {
    echo "优秀\n";
} elseif ($score >= 80) {
    echo "良好\n";
} elseif ($score >= 60) {
    echo "及格\n";
} else {
    echo "不及格\n";
}
?>

<?php
$day = 4;
switch ($day) {
    case 1: echo "星期一\n"; break;
    case 2: echo "星期二\n"; break;
    case 3: echo "星期三\n"; break;
    case 4: echo "星期四\n"; break;
    case 5: echo "星期五\n"; break;
    case 6: echo "星期六\n"; break;
    case 7: echo "星期日\n"; break;
    default: echo "无效输入\n";
}
?>

<?php
$code = 404;
$desc = match ($code) {
    200, 201 => "成功",
    301, 302 => "重定向",
    400, 403, 404 => "客户端错误",
    500, 502, 503 => "服务器错误",
    default => "未知状态",
};
echo "状态码 $code：$desc\n";
?>

<?php
$sum = 0;
for ($i = 1; $i <= 100; $i++) {
    $sum += $i;
}
echo "1 到 100 的和：" . $sum . "\n";
?>

<?php
for ($i = 1; $i <= 9; $i++) {
    $row = "";
    for ($j = 1; $j <= $i; $j++) {
        $row .= "{$j}x{$i}=" . ($i * $j) . "  ";
    }
    echo $row . "\n";
}
?>

<?php
$scores = [55, 90, 72, 88, 45];
foreach ($scores as $index => $score) {
    if ($score < 60) {
        continue;
    }
    echo "索引 $index 成绩 $score 及格\n";
}
?>

<?php
$i = 1;
while ($i <= 20) {
    if ($i === 15) {
        break;
    }
    if ($i % 3 === 0) {
        echo $i . "\n";
    }
    $i++;
}
?>

<?php
function add($a, $b) {
    return $a + $b;
}
echo "add(10, 20) = " . add(10, 20) . "\n";
echo "add(3.5, 2.5) = " . add(3.5, 2.5) . "\n";
?>

<?php
function greet($name, $greeting = "你好") {
    return "$greeting，$name！";
}
echo greet("小明") . "\n";
echo greet("小红", "早上好") . "\n";

function sumAll(...$nums) {
    return array_sum($nums);
}
echo "sumAll(1,2,3) = " . sumAll(1, 2, 3) . "\n";
echo "sumAll(1,2,3,4,5) = " . sumAll(1, 2, 3, 4, 5) . "\n";
?>

<?php
declare(strict_types=1);

function calculate(int $a, int $b): int {
    return $a * $b + 10;
}
echo calculate(4, 5) . "\n"; // 30
// echo calculate("4", 5); // 严格模式下会报错
?>

<?php
$fruits = ["苹果", "香蕉"];
$fruits[] = "橙子";
array_unshift($fruits, "葡萄");
echo "数量：" . count($fruits) . "\n";
print_r($fruits);
unset($fruits[0]);
echo "是否含香蕉：" . (in_array("香蕉", $fruits) ? "是" : "否") . "\n";
?>

<?php
$scores = [
    "语文" => 90,
    "数学" => 85,
    "英语" => 92,
];
echo "数学成绩：" . $scores["数学"] . "\n";
$scores["物理"] = 88;
foreach ($scores as $subject => $score) {
    echo "$subject：$score 分\n";
}
?>

<?php
$nums = [3, 1, 4, 1, 5, 9, 2, 6];
$unique = array_unique($nums);
sort($unique);
print_r($unique);
$descs = array_map(fn($n) => "数字$n", $unique);
echo implode("，", $descs) . "\n";
echo "最大值：" . max($nums) . "，最小值：" . min($nums) . "\n";
?>

<?php
$a = [1, 2, 3];
$b = [3, 4, 5];
$merged = array_merge($a, $b);
echo "合并：" . implode(",", $merged) . "\n";

$words = ["php", "js", "php", "go", "php"];
$freq = array_count_values($words);
print_r($freq);

$even = array_filter($merged, fn($n) => $n % 2 === 0);
echo "偶数：" . implode(",", $even) . "\n";
?>

<?php
$s = " Hello, PHP ";
echo "trim：" . trim($s) . "\n";
echo "大写：" . strtoupper(trim($s)) . "\n";
echo "替换：" . str_replace("PHP", "Hypertext Preprocessor", trim($s)) . "\n";
$parts = explode(",", trim($s));
print_r($parts);
echo "拼接：" . implode(" | ", $parts) . "\n";
?>

<?php
$text = "PHP 是最好的语言之一，PHP 语法灵活。";
echo "PHP 首次出现位置：" . strpos($text, "PHP") . "\n";
echo "PHP 出现次数：" . substr_count($text, "PHP") . "\n";
echo "截取前 9 个字符：" . substr($text, 0, 9) . "\n";
echo "包含 PHP：" . (str_contains($text, "PHP") ? "是" : "否") . "\n";
?>

<?php
$email = "user@example.com";
if (preg_match("/^[\w.-]+@[\w.-]+\.\w+$/", $email)) {
    echo "邮箱格式正确\n";
} else {
    echo "邮箱格式错误\n";
}

$text = "订单号 123，金额 45.6 元";
echo preg_replace("/\d+/", "#", $text) . "\n";

$csv = "php,go|rust;elixir";
$langs = preg_split("/[,|;]/", $csv);
print_r($langs);
?>

<?php
$pi = 3.1415926;
printf("保留两位：%.2f\n", $pi);
printf("补零五位：%05d\n", 42);
printf("左对齐：%-8s|\n", "PHP");
$formatted = sprintf("价格：￥%.2f", 59.9);
echo $formatted . "\n";
?>

<?php
class Student {
    public $name;
    public $score;

    public function __construct($name, $score) {
        $this->name = $name;
        $this->score = $score;
    }

    public function getInfo() {
        return "{$this->name}，成绩 {$this->score} 分";
    }
}

$stu = new Student("小明", 92.5);
echo $stu->getInfo() . "\n";
?>

<?php
class Animal {
    protected $name;

    public function __construct($name) {
        $this->name = $name;
    }

    public function speak() {
        return "动物叫声";
    }
}

class Dog extends Animal {
    public function speak() {
        return parent::speak() . "：汪汪！";
    }
}

$dog = new Dog("旺财");
echo $dog->speak() . "\n";
?>

<?php
class BankAccount {
    private float $balance = 0;

    public function deposit(float $amount): void {
        if ($amount > 0) {
            $this->balance += $amount;
        }
    }

    public function withdraw(float $amount): bool {
        if ($amount > 0 && $amount <= $this->balance) {
            $this->balance -= $amount;
            return true;
        }
        return false;
    }

    public function getBalance(): float {
        return $this->balance;
    }
}

$acc = new BankAccount();
$acc->deposit(1000);
$acc->withdraw(300);
echo "余额：" . $acc->getBalance() . "\n";
?>

<?php
interface Shape {
    public function area(): float;
}

class Circle implements Shape {
    public function __construct(private float $radius) {}
    public function area(): float {
        return 3.14159 * $this->radius ** 2;
    }
}

class Square implements Shape {
    public function __construct(private float $side) {}
    public function area(): float {
        return $this->side ** 2;
    }
}

$shapes = [new Circle(3), new Square(5)];
$total = 0;
foreach ($shapes as $shape) {
    $total += $shape->area();
}
printf("总面积：%.2f\n", $total);
?>

<?php
$name = $_GET["name"] ?? "游客";
$lang = $_GET["lang"] ?? "zh";
if ($lang === "zh") {
    echo "你好，$name！\n";
} else {
    echo "Hello, $name!\n";
}
?>

<?php
if ($_SERVER["REQUEST_METHOD"] === "POST") {
    $username = htmlspecialchars($_POST["username"] ?? "");
    $password = $_POST["password"] ?? "";
    if ($username === "" || $password === "") {
        echo "用户名和密码不能为空\n";
    } else {
        echo "欢迎，$username！密码长度：" . strlen($password) . "\n";
    }
} else {
    echo "请使用 POST 提交表单\n";
}
?>

<?php
session_start();
$_SESSION["user_id"] = 1;
$_SESSION["username"] = "admin";
echo "已写入 Session\n";
echo "当前用户：" . ($_SESSION["username"] ?? "未登录") . "\n";
unset($_SESSION["username"]);
echo "注销后：" . ($_SESSION["username"] ?? "未登录") . "\n";
session_destroy();
?>

<?php
// 模拟表单：<input type="file" name="avatar">
if (isset($_FILES["avatar"])) {
    $file = $_FILES["avatar"];
    if ($file["error"] !== UPLOAD_ERR_OK) {
        echo "上传失败，错误码：" . $file["error"] . "\n";
    } elseif ($file["size"] > 2 * 1024 * 1024) {
        echo "文件超过 2MB\n";
    } else {
        $ext = strtolower(pathinfo($file["name"], PATHINFO_EXTENSION));
        if (!in_array($ext, ["jpg", "png", "gif"])) {
            echo "仅支持 jpg/png/gif\n";
        } else {
            $dest = "uploads/" . uniqid() . "." . $ext;
            move_uploaded_file($file["tmp_name"], $dest);
            echo "上传成功：" . $dest . "\n";
        }
    }
}
?>

<?php
$file = "data.txt";
file_put_contents($file, "Hello PHP File System\n第二行");
$content = file_get_contents($file);
echo "文件内容：\n" . $content;
echo "文件大小：" . filesize($file) . " 字节\n";
?>

<?php
$dir = "docs";
if (!is_dir($dir)) {
    mkdir($dir);
    file_put_contents("$dir/a.txt", "A");
    file_put_contents("$dir/b.txt", "B");
}
$items = scandir($dir);
$count = 0;
foreach ($items as $item) {
    if ($item === "." || $item === "..") {
        continue;
    }
    $path = "$dir/$item";
    if (is_file($path)) {
        echo "$item：" . filesize($path) . " 字节\n";
        $count++;
    }
}
echo "文件总数：$count\n";
?>

<?php
$user = [
    "id" => 1,
    "name" => "Alice",
    "tags" => ["admin", "dev"],
];
$json = json_encode($user, JSON_UNESCAPED_UNICODE);
echo "JSON：" . $json . "\n";
$back = json_decode($json, true);
echo "姓名：" . $back["name"] . "\n";
echo "标签数：" . count($back["tags"]) . "\n";
echo "JSON 错误：" . json_last_error_msg() . "\n";
?>

<?php
$students = [
    ["张三", 90],
    ["李四", 85],
    ["王五", 78],
];
$handle = fopen("students.csv", "w");
foreach ($students as $row) {
    fputcsv($handle, $row);
}
fclose($handle);

$handle = fopen("students.csv", "r");
echo "CSV 内容：\n";
while (($row = fgetcsv($handle)) !== false) {
    echo $row[0] . "：" . $row[1] . " 分\n";
}
fclose($handle);
?>

<?php
try {
    $pdo = new PDO(
        "mysql:host=localhost;dbname=test;charset=utf8mb4",
        "root",
        "password",
        [PDO::ATTR_ERRMODE => PDO::ERRMODE_EXCEPTION]
    );
    echo "数据库连接成功\n";
    $version = $pdo->query("SELECT VERSION()")->fetchColumn();
    echo "MySQL 版本：" . $version . "\n";
} catch (PDOException $e) {
    echo "连接失败：" . $e->getMessage() . "\n";
}
?>

<?php
$pdo = new PDO("mysql:host=localhost;dbname=test;charset=utf8mb4", "root", "password");
$sql = "INSERT INTO users (name, email) VALUES (?, ?)";
$stmt = $pdo->prepare($sql);
$users = [
    ["Alice", "alice@example.com"],
    ["Bob", "bob@example.com"],
];
foreach ($users as $user) {
    $stmt->execute($user);
    echo "插入成功，ID：" . $pdo->lastInsertId() . "\n";
}
?>

<?php
$pdo = new PDO("mysql:host=localhost;dbname=test;charset=utf8mb4", "root", "password");
$stmt = $pdo->query("SELECT id, name, email FROM users ORDER BY id");
$users = $stmt->fetchAll(PDO::FETCH_ASSOC);
echo "共 " . count($users) . " 个用户：\n";
foreach ($users as $user) {
    echo "#{$user['id']} {$user['name']} ({$user['email']})\n";
}
?>

<?php
$pdo = new PDO("mysql:host=localhost;dbname=test;charset=utf8mb4", "root", "password");
$update = $pdo->prepare("UPDATE users SET email = ? WHERE id = ?");
$update->execute(["new@example.com", 1]);
echo "更新行数：" . $update->rowCount() . "\n";

$delete = $pdo->prepare("DELETE FROM users WHERE id = ?");
$delete->execute([2]);
echo "删除行数：" . $delete->rowCount() . "\n";
?>

<?php
$messages = [];

function addMessage(&$messages, $author, $content) {
    array_unshift($messages, [
        "author" => $author,
        "content" => $content,
        "time" => date("Y-m-d H:i:s"),
    ]);
}

function listMessages($messages) {
    if (count($messages) === 0) {
        echo "暂无留言\n";
        return;
    }
    foreach ($messages as $msg) {
        echo "[{$msg['time']}] {$msg['author']}：{$msg['content']}\n";
    }
}

addMessage($messages, "小明", "第一条留言");
addMessage($messages, "小红", "PHP 真好学");
listMessages($messages);
?>

<?php
function validateRegister(array $data): array {
    $errors = [];
    $username = $data["username"] ?? "";
    $password = $data["password"] ?? "";
    $email = $data["email"] ?? "";

    if (strlen($username) < 3 || strlen($username) > 20) {
        $errors[] = "用户名长度需在 3-20 之间";
    }
    if (strlen($password) < 8 || !preg_match("/\d/", $password)) {
        $errors[] = "密码至少 8 位且包含数字";
    }
    if (!preg_match("/^[\w.-]+@[\w.-]+\.\w+$/", $email)) {
        $errors[] = "邮箱格式不正确";
    }
    return $errors;
}

$data = ["username" => "ab", "password" => "abc12345", "email" => "bad"];
$errors = validateRegister($data);
echo empty($errors) ? "校验通过\n" : implode("；", $errors) . "\n";
?>

<?php
class CartItem {
    public function __construct(
        public string $name,
        public float $price,
        public int $qty = 1
    ) {}
    public function subtotal(): float {
        return $this->price * $this->qty;
    }
}

class Cart {
    private array $items = [];

    public function add(CartItem $item): void {
        $this->items[] = $item;
    }

    public function total(): float {
        $sum = 0;
        foreach ($this->items as $item) {
            $sum += $item->subtotal();
        }
        return $sum;
    }

    public function list(): void {
        foreach ($this->items as $item) {
            printf("%s x%d = %.2f 元\n", $item->name, $item->qty, $item->subtotal());
        }
    }
}

$cart = new Cart();
$cart->add(new CartItem("PHP 教程", 59, 2));
$cart->add(new CartItem("编程鼠标", 129, 1));
$cart->list();
printf("总计：%.2f 元\n", $cart->total());
?>

<?php
$file = "tasks.json";

function loadTasks(string $file): array {
    if (!file_exists($file)) {
        return [];
    }
    return json_decode(file_get_contents($file), true) ?? [];
}

function saveTasks(string $file, array $tasks): void {
    file_put_contents($file, json_encode($tasks, JSON_UNESCAPED_UNICODE | JSON_PRETTY_PRINT));
}

$tasks = loadTasks($file);
$tasks[] = ["id" => count($tasks) + 1, "title" => "学习 PHP 面向对象", "done" => false];
$tasks[] = ["id" => count($tasks) + 1, "title" => "练习 PDO 操作", "done" => false];
saveTasks($file, $tasks);

$pending = array_filter($tasks, fn($t) => !$t["done"]);
echo "未完成任务：\n";
foreach ($pending as $task) {
    echo "- [{$task['id']}] {$task['title']}\n";
}
?>