php - 帮我看看，这段数据库连接代码有没有什么问题？

Question

新手学php，书上一直没有好的例子，网上的也有错误，自己照着php手册写了一个完整点的
高手帮我看一下，有没有哪里写错了...谢谢了

//面向对象
$mysqli = new mysqli("localhost", "user", "pass", "database");  
if(mysqli_connect_errno())) {  //这边判断方式和下面面向过程中的直接判断变量有什么区别？
    printf("Connect failed: %s\n",  mysqli_connect_error());
    exit();
}
$query =  "SELECT `name`, `address`, `phone` FROM Users WHERE gender=? AND age=?";
if($stmt = $mysqli->prepare($query) {
    $stmt->bind_param("si", $gender, $age);  //这边插入参数是不是写在这里？
    $stmt->execute();
    $stmt->bind_result($name, $address, $phone);
     
    while($stmt->fetch()) {
         printf ("%s (%s,%s)<br />", $name, $address, $phone); 
    }
    $stmt->close();
}
$mysqli->close();
 
/面向过程
$mysqli = mysqli_connecti("localhost", "user", "pass", "database");
if(!$mysqli) {
    printf ("Connect failed: %s\n",  mysqli_connect_error());
    exit();
}
$query =  "SELECT `name`, `address`, `phone` FROM Users WHERE gender=? AND age=?";
if ($stmt = mysqli_prepare($query)){
    mysqli_stmt_bind_param($stmt, "si", $gender, $age);
    mysqli_stmt_execute($stmt);
    mysqli_stmt_bind_result($stmt, $name, $address, $phone);
     
    while (mysqli_stmt_fetch($stmt)) {
        printf ("%s (%s,%s)<br />", $name, $address, $phone); 
    }
    mysqli_stmt_close($stmt);
}
$mysqli_close();

Answer 1

代码是写出来跑的，代码写的对不对，得问编译器或者解析器，它们才是真正的老师。

Answer 2

这肉眼真不好看,最后一句好像有问题, 得传入参数($mysqli)吧.

Answer 3

prepare+execute后bind_result+循环fetch是传统的做法.
PHP从5.4开始底层默认采用mysqlnd实现mysql,mysqli,pdo_mysql.
这时你可以使用 get_result 和 fetch_all 快速拿到查询结果.
prepare+execute后 $stmt->get_result()->fetch_all(MYSQLI_ASSOC) 即可拿到结果集.
比如:

post.php?id=1024

MySQLi普通查询:
$db = new mysqli('127.0.0.1','user','pass','dbname',3306);
var_export($db->query('SELECT * FROM posts WHERE id='.intval($_GET['id']))->fetch_all());

MySQLi预处理绑定参数查询:
$db = new mysqli('127.0.0.1','user','pass','dbname',3306);
$stmt = $db->prepare('SELECT * FROM posts WHERE id=?'); //预处理
$stmt->bind_param('i', $_GET['id']); //绑定参数(可以防止SQL注入)
$stmt->execute(); //查询
var_export($stmt->get_result()->fetch_all());