Global database connection inside functions - php

Question

Trying to global database connection in all functions in a .php file.
sql.php:
<?php
$servername = "XXXXX";
$username = "XXXXX";
$password = "XXXXX";
$dbname = "XXXXX";
$conn = new mysqli($servername, $username, $password, $dbname);
mysqli_set_charset($conn, "utf8");
if ($conn->connect_error) {
die("Connection failed: " . $conn->connect_error);
}
?>
save.php
$conn = require_once('../path/to/sql.php');
function save()
{
global $conn;
$sql = "INSERT INTO `content` (title, text, cat)
VALUES ('".$_POST["title"]."', '".$_POST["text"]."', '".$_POST["category"]."')";
if ($conn->query($sql) === TRUE) {
show();
}
$conn->close();
}
well i want to get sql.php with require_once and then make it global then put this in save() function.
error is:
Fatal error: Call to a member function query() on a non-object in
/homepages/3/xxxxxxxx/htdocs/xxxxxxxx/xxxxxxxx/content.php on line 37
actually i don't know this way to make it global is correct or not, so please help me to choose best way to make a global database connection inside the functions.

Answer 1

Try
define('DATABASE_USERNAME', 'root');
define('DATABASE_PASSWORD', 'password');
define('DATABASE_HOST', 'localhost');
define('DATABASE_DBNAME', 'db');
$conn = new mysqli(DATABASE_HOST, DATABASE_USERNAME, DATABASE_PASSWORD, DATABASE_DBNAME);
Named constants are great for static global data.
Also you just need to do
require_once 'path/to/sql.php';
And not
$conn = require_once 'path/to/sql.php';
$conn is already being set in your require_once.