db.php

<?php

function db_connect() {

    // Define connection as a static variable, to avoid connecting more than once 
    static $connection;

    // Try and connect to the database, if a connection has not been established yet
    if(!isset($connection)) {
         // Load configuration as an array. Use the actual location of your configuration file
        $config = parse_ini_file('config.ini'); 
        $connection = mysqli_connect($config['server'],$config['username'],$config['password'],$config['dbname']);
    }

    // If connection was not successful, handle the error
    if($connection === false) {
        // Handle error - notify administrator, log to a file, show an error screen, etc.
        return mysqli_connect_error(); 
    }
    return $connection;
}

function db_query($query) {
    // Connect to the database
    $connection = db_connect();

    // Query the database
    $result = mysqli_query($connection,$query);

    return $result;
}

function db_select($query) {
    $rows = array();
    $result = db_query($query);

    // If query failed, return `false`
    if($result === false) {
        return false;
    }

    // If query was successful, retrieve all the rows into an array
    while ($row = mysqli_fetch_assoc($result)) {
        $rows[] = $row;
    }
    return $rows;
}

function db_select_single_row($query) {
    $rows = array();
    $result = db_query($query);

    // If query failed, return `false`
    if($result === false) {
        return false;
    }

    // If query was successful, retrieve all the rows into an array
    $row = mysqli_fetch_assoc($result);
    
    return $row;
}

function db_quote($value) {
    $connection = db_connect();
    return "'" . mysqli_real_escape_string($connection,$value) . "'";
}