PHP错误：为什么这不工作，我不能在我的页面中看到数据结果？

Question

我正在设置一个新的wampserver，并使用名为“users”的表创建了一个新的数据库

apache 2.4.23

<?php

    $server = 'localhost';
    $serverUsername = 'root';
    $serverPassword = '';
    $dbName = 'test';

    $connection = mysqli_connect($server,$serverUsername,$serverPassword);
    msqli_select_db($dbName);
    if(!$connection){
        echo 'connection failed to database '.mysqli_connect_error();
    }
    $sql = "SELECT * FROM users";
    $query = mysqli_query($sql);
    while($row = mysqli_fetch_array($query)){
        print_r($row);
    }

?>

我的值实际上在数据库中，但在运行代码后页面中没有显示任何内容

Answer 1

请查看有关修复的注释

$server = 'localhost';
$serverUsername = 'root';
$serverPassword = '';
$dbName = 'test';

// FIX 1
// You need to mention the database name as the last argument
$connection = mysqli_connect($server,$serverUsername,$serverPassword, $dbName);
if(!$connection){
    echo 'connection failed to database '.mysqli_connect_error();
}

$sql = "SELECT * FROM users";

// FIX 2
// The first argument should be your mysqli connection
$query = mysqli_query($connection, $sql);

// Check for errors
if (!$query) {
    printf("Error: %s\n", mysqli_error($connection));
    exit();
}

while($row = mysqli_fetch_array($query)){
    print_r($row);
}

?>

mysqli_connect的参考：https://secure.php.net/manual/en/function.mysqli-connect.php

mysqli\u查询的参考文件：https://secure.php.net/manual/en/mysqli.query.php