Why isn't my PHP able to connect to MySQL?

Question

I am trying to connect to my MySQL database using the following PHP code

<?php

require "credentials.php";

$conn = mysqli_connect($hostname, $username, $password, $databaseName);

if(mysqli_connect_errno())
{
echo "Failed to connect to MySQL: " . mysqli_connect_error();
}

?>

And I am getting the following output:

Failed to connect to MySQL: Connection refused

What could be the reasons that this is happening, and how can I fix it?

Thanks in advance.

Answer 1

from your code it seems that you are using undefined variables to connect to database. if you load them from external file, than use something like this in that file:

define("DBPASSWORD", "database_pass");
define("DBUSERNAME", "databaseusername");
define("DBNAME", "database");
define("DBHOST", "database_host");

and than use in file you shown us:

$conn = mysqli_connect(DBHOST, DBUSERNAME, DBPASSWORD, DBNAME);

OR another way, the way I can't recomend is using globals.

WARNING: I discourage using globals, when not needed.

Your credentials.php should look like that:

global $databaseName;
global $password;
global $username;
global $username;
$databaseName= "db_name";
$password= "db_password";
$username= "db_username";
$hostname= "db_host";

and than in other places, first you need to call the globals before usage.

require "credentials.php";

global $databaseName;
global $password;
global $username;
global $username;

$conn = mysqli_connect($hostname, $username, $password, $databaseName);