PHP 错误：为什么这不起作用，我在我的页面中看不到数据结果？

Question

我正在设置一个新的 wampserver 并创建了一个新数据库，其中包含一个名为“users”的表

apache 2.4.23 & PHP 7.1.10 & mySQL 5.7.14

<?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);
    }

?>

我的值确实在数据库中，但运行代码后页面中没有显示任何内容

Answer 1

看看提到修复的评论

$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参考： https : mysqli_connect

mysqli_query参考： https : //secure.php.net/manual/en/mysqli.query.php