在Select SQL查询中使用PHP变量，它返回Error [duplicate]

Question

This question already has an answer here:

• When to use single quotes, double quotes, and backticks in MySQL 12 answers
• Are you allowed to use numbers as table names in MySQL? 5 answers

I am new to PHP and MySQL and I am trying to use PHP Variable as name of table. But when I do that it returns :

SQL Error: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near '321321' at line 1

My code is :

$dbname = "321321";
require_once('authenticate.php');
$ownerID =  $_SESSION["accNumber"];
if($dbname != $ownerID){
    header('Location: login.php');
}


$db_host = 'localhost'; // Server Name
$db_user = 'root'; // Username
$db_pass = '***'; // Password
$db_name = 'test_database'; // Database Name

$conn = mysqli_connect($db_host, $db_user, $db_pass, $db_name);
if (!$conn) {
    die ('Failed to connect to MySQL: ' . mysqli_connect_error());
}



$sql = 'SELECT * FROM '.$dbname.'';
$query = mysqli_query($conn, $sql);

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Answer 1

You should add backticks ` around your table name, because it doesn't begin by a letter :

$sql = 'SELECT * FROM `'.$dbname.'`';

As pointed by @RacilHilan (see comment below), it would be better to rename the table to avoid this kind of confusions.