如何在 PHP 中连接到 MySQL 数据库

Question

I'm kinda new in PHP, but I was told to create a login form that connects to Mysql database.

I tried the following code to connect to the database, tried it with, and without the database. I tried mysql_connect and something else, but always got the same error: (hidden:servername and others are the proper information of the server, just it is not pulbic.)

Fatal error: Uncaught Error: Call to undefined function mysqli() in C:\\Users\\vg141fy\\login\\login.php:25 Stack trace: #0 {main} thrown in C:\\Users\\vg141fy\\login\\login.php on line 25

<?php
    if (ISSET($_POST["submit"]))
    {
        $servername = "hidden:servername";
        $username = "hidden:username";
        $password = "hidden:password";
        $database = "hidden:database";

        $conn= mysqli($servername, $username, $password, $database);
    }
?>

I open a localhost to open my php pages with "php -S localhost:4000", but i don't use XAMPP. Should I use it, or is there something else that is miss?

Answer 1

Look at the quick start guide .

If you are using the OO interface, you need to include the new keyword.

$conn = new mysqli($servername, $username, $password, $database);

If you are using the procedural interface, then you need to use the mysqli_connect function.

$conn = mysqli_connect($servername, $username, $password, $database);

Answer 2

You have to check first that connection successfully established or not
use this to connect your database using this

<?php
$servername = "localhost";
$username = "username";
$password = "password";
$dbname = "myDB";

// Create connection
$conn = new mysqli($servername, $username, $password, $dbname);

// Check connection
if ($conn->connect_error) {
    die("Connection failed: " . $conn->connect_error);
} 
else{
    echo "success";
}

?>

if it give success message then error should be in your after connection code so try to create table and check

Answer 3

Try to change database credential below and ensure that it matches yours.

If the connection failed it will print error below could not connect to database .

  <?php
     $dbhost = 'localhost';
     $dbuser = 'your-db-username';
     $dbpass = 'your-db-pass';
     $conn = mysqli_connect($dbhost, $dbuser, $dbpass);

     if(! $conn ){
        //die('Could not connect: ' . mysqli_error());
    echo 'Could not connect to database ';
     }

     echo 'Connected successfully';
     mysqli_close($conn);
  ?>