define("a", "hello");
echo a;

    $a = 111;
    $b = '111abc';
    echo $a + $b;

    $c = 'abc123';
    $d = '123abc';
    echo '<br />', (int)$c, '<br />',  (int)$d;

    $a = 'wdnmd';
    var_dump(is_int($a), is_string($a));

    $a = '1.1abc';
    echo gettype($a);

    $a = '1.1abc';
    echo settype($a, 'int');

echo file_get_contents("test.txt");

$变量 = json_decode(Json数据, true);

$变量 = parse_ini_file("文件位置", true);

    $str = "wdwafu%dwajdi";
    echo strrpos($str, '%');

echo substr('abcdef', 1);      //输出 bcdef
echo substr('abcdef', 1, 2);   //输出 bc
echo substr('abcdef', -3, 2);  //输出 de
echo substr('abcdef', 1, -2);  //输出 bcd

class db
{
    // 连接地址
    public $host = "mysql:host=localhost;dbname=test;";
    // 账号
    public $name = "root";
    // 密码
    public $password = "20181119";

    // 数据库实例
    public $pdo;

    /**
     * 连接
     * db constructor.
     */
    public function __construct() {
        try {
            $this->pdo = new PDO($this->host, $this->name, $this->password);
        } catch (PDOException $e) {
            echo $e;
            die();
        }
    }

    /**
     * 查询
     * @param $sql
     * @return array|false|PDOStatement|null
     */
    public function select($sql) {
        $res = $this->pdo->query($sql);
        if(!$res) {
            return $res;
        }
        return $res->fetchAll(PDO::FETCH_ASSOC);
    }

    /**
     * 增删改
     * @param $sql
     * @return bool
     */
    public function exc($sql) {
        $res = $this->pdo->exec($sql);
        if ($res == 0) {
            return false;
        }
        return true;
    }
}

$servername = "localhost";
$username = "username";
$password = "password";
 
// 创建连接
$conn = new mysqli($servername, $username, $password);
 
// 检测连接
if ($conn -> connect_error)
{
    die("连接失败: " . mysqli_connect_error());
} 
else
{
    echo "连接成功";
}

//关闭连接
mysqli_close($conn);

$conn = new mysqli(地址,用户名,密码,数据库名);

$sql = "create table lovexhj(
    id int primary key,
    name varchar(30) not null,
    age int not null
)";

if($conn -> query($sql) === true)
{
    echo "<br />" . "数据表创建成功！";
}
else
{
    echo "<br />" . "错误！" . $conn -> error;
}

$sql = "create table lovexhj(
    id int primary key,
    name varchar(30) not null,
    age int not null
)";

if($conn -> query($sql) === true)
{
    echo "<br />" . "数据表创建成功！";
}
else
{
    echo "<br />" . "错误！" . $conn -> error;
}

$sql = "insert lovexhj(id, name, age) values(2, '闸总', 18);";
$sql .= "insert lovexhj(id, name, age) values(3, '闸总', 18);";
$sql .= "insert lovexhj(id, name, age) values(4, '闸总', 18);";
if($conn -> multi_query($sql) === true)
{
    echo "<br />" . "数据插入成功！";
}
else
{
    echo "<br />" . "错误！" . $conn -> error;
}

//预处理语句
$sql = $conn -> prepare("insert lovexhj values(?, ?, ?);");
$sql -> bind_param("isi", $a, $b, $c);

//设置参数
$a = "1";
$b = "wdnmd1";
$c = "18";
//执行
$sql -> execute();

$a = "2";
$b = "wdnmd2";
$c = "18";
$sql -> execute();

$a = "3";
$b = "wdnmd3";
$c = "18";
$sql -> execute();

echo "<br />插入成功！";

//关闭
$sql -> close();

$sql = "select * from lovexhj;";
$result = $conn -> query($sql);

if($result -> num_rows > 0)
{
    while($row = $result -> fetch_assoc())
    {
        echo "ID:" . $row["id"] . " - " . "Name:" . $row["name"] . " - " . "age:" . $row["age"] . "<br>";
    }
}
else
{
    echo "没有数据";
}

// 设置 cookie
setcookie("test", "Test");
// 设置一小时内的 cookie
setcookie("test", "Test", time() + 3600);
// 存入数组
$arr = ["123", "456"];
setcookie("arr", serialize($arr));
// 取出数据
var_dump(unserialize($_COOKIE("arr")));