Examples of mysqli for personal reference

mysqli.php

<?php

/**
 * These variables (strings) contain data to connect to the database
 */
$hostname = "";
$username = "";
$password = "";
$database = "";

/**
 * Establishes a connection with the database
 */
$mysqli = new mysqli($this->hostname, $this->username, $this->password, $this->database);
if($mysqli->connect_errno > 0){
	die('Unable to connect to database [' . $mysqli->connect_error . ']');
}
return $mysqli;

/**
 * Retrieveing multiple things
 */
$result = $mysqli->query("SELECT * FROM posts ORDER BY id DESC");
$posts = array();
while($row = $result->fetch_assoc()) {
	$post =  new Post($row);
	$posts[] = $post;
}

/**
 * Getting one thing
 */
$result = $mysqli->query("SELECT name FROM categories WHERE id =".$id);
$row = $result->fetch_assoc();
return $row['name'];