Please help me see if there is anything wrong with this database connection code?

I am a novice learning PHP. There are no good examples in books, and there are also mistakes on the Internet. I wrote a complete one according to the PHP manual
Experts can help me take a look and see if there are any mistakes...Thank you

<code>//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();</code>

Reply content:

I am a novice learning PHP. There are no good examples in books, and there are also mistakes on the Internet. I wrote a complete one according to the PHP manual
Experts can help me take a look and see if there are any mistakes...Thank you

<code>//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();</code>

Code is written and run. Whether the code is written correctly or not, you have to ask the compiler or parser, they are the real teachers.

Run it yourself. . .

This doesn’t look good to the naked eye. There seems to be something wrong with the last sentence. You have to pass in the parameter ($mysqli).

bind_result+loop fetch after prepare+execute is the traditional approach.
Starting from PHP 5.4, the bottom layer uses mysqlnd by default to implement mysql, mysqli, pdo_mysql.
At this time, you can use get_result and fetch_all to quickly get the query results.
After prepare+execute $stmt->get_result()->fetch_all(MYSQLI_ASSOC) You can get the result set.
For example:

<code>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());</code>