无法访问数据库[重复]

Question

您好，我需要一些帮助来编写 php 代码以连接数据库 我的源代码是

$host="127.0.0.1"; // Host name 

$username="root"; // Mysql username 

$password=""; // Mysql password 

$db_name="test"; // Database name 

$tbl_name="forum_question"; // Table name 

// Connect to server and select databse.
`mysqli_connect("$host", "$username", "$password")or die("cannot connect"); 
mysqli_select_db("$db_name")or die("cannot select DB");
$sql="SELECT * FROM $tbl_name ORDER BY id DESC";`

但是显示错误

警告：mysqli_select_db() 需要 2 个参数，1 个在 C:\xampp\htdocs\123\tryforum\main_forum.php 第 11 行给出 无法选择数据库

如何解决

Answer 1

您需要将连接变量传递给 mysqli_select_db。 See this link

$host="127.0.0.1"; // Host name 

$username="root"; // Mysql username 

$password=""; // Mysql password 

$db_name="test"; // Database name 

$tbl_name="forum_question"; // Table name 

// Connect to server and select databse.
$con = mysqli_connect("$host", "$username", "$password") or die("cannot connect"); 
mysqli_select_db($con, "$db_name")or die("cannot select DB");

$sql="SELECT * FROM $tbl_name ORDER BY id DESC";`

Answer 2

mysqli_select_db()

需要两个参数，首先是您的数据库连接，其次是您的 数据库名称

$conn=mysqli_connect("$host", "$username", "$password")or die("cannot connect"); 
mysqli_select_db($conn,"$db_name")or die("cannot select DB");
$sql="SELECT * FROM $tbl_name ORDER BY id DESC";
$result=mysqli_query($conn,$sql);