<?php

class DB {

    private $_dbhost = DBHOST;
    private $_dbuser = DBUSER;
    private $_dbpass = DBPASS;
    private $_dbname = DBNAME;
    private $_dbchar = DBCHAR;

    private static $_instance = null;

    public $_connection;
    public $_prefix;
    public $_query;
    public $_error = [];
    public $_result = [];
    public $_count = 0;
    public $_affected_rows = 0;
    public $_columns;
    public $_operators = [
        '=', '<', '>', '<=', '>=', '<>', '!=', '<=>',
        'like', 'like binary', 'not like', 'between', 'ilike',
        '&', '|', '^', '<<', '>>',
        'rlike', 'regexp', 'not regexp',
        '~', '~*', '!~', '!~*', 'similar to',
        'not similar to', 'not ilike', '~~*', '!~~*',
    ];

    public static function getInstance()
    {
        if (!self::$_instance) {
            self::$_instance = new self();
        }
        return self::$_instance;
    }

    public function __construct() {
        $this->_connection = new mysqli($this->_dbhost, $this->_dbuser, $this->_dbpass, $this->_dbname);
        if (mysqli_connect_errno()) {
            trigger_error('Database connection failed: ' . mysqli_connect_error(), E_USER_ERROR);
        }
        $this->_connection->set_charset($this->_dbchar);
    }

    public function safe($var)
    {
        $data = @unserialize($var);
        if ($data === false) {
            $var = $this->_connection->real_escape_string(trim($var));
        }
        return $var;
    }

    public function prefix($prefix)
    {
        $this->_prefix = $this->safe($prefix);
    }

    public function table($table)
    {
        $this->_table = $this->safe($table);
        return $this;
    }

    public function error($message)
    {
        $this->_error[] = $message;
    }

    public function getError()
    {
        $number = 1;
        $log = '';
        foreach ($this->_error as $error) {
            $log .= "#" . $number . ": " . $error . "<br />";
            $number++;
        }
        return $log;
    }
}