amazing codeigntier functions

<?php

define('FILE_READ_MODE', 0644);
define('FILE_WRITE_MODE', 0666);
define('DIR_READ_MODE', 0755);
define('DIR_WRITE_MODE', 0777);

define('FOPEN_READ', 'rb');
define('FOPEN_READ_WRITE', 'r+b');
define('FOPEN_WRITE_CREATE_DESTRUCTIVE', 'wb'); // truncates existing file data, use with care
define('FOPEN_READ_WRITE_CREATE_DESTRUCTIVE', 'w+b'); // truncates existing file data, use with care
define('FOPEN_WRITE_CREATE', 'ab');
define('FOPEN_READ_WRITE_CREATE', 'a+b');
define('FOPEN_WRITE_CREATE_STRICT', 'xb');
define('FOPEN_READ_WRITE_CREATE_STRICT', 'x+b');

define('IS_AJAX', isset($_SERVER['HTTP_X_REQUESTED_WITH']) && strtolower($_SERVER['HTTP_X_REQUESTED_WITH']) == 'xmlhttprequest');
define('CHARSET', 'UTF-8');
define('CHARSET_NAMES', 'utf8');
define('CHARSET_COLLATION', 'utf8_general_ci');

//////////////////////////////////////////////////////////////////////////////

if (isset($_SERVER['HTTP_HOST'])) {
    if (
            (strpos($_SERVER['HTTP_HOST'], '.') === FALSE) || //from my computer
            (substr($_SERVER['HTTP_HOST'], 0, 8) === '192.168.') || //from private ip address
            ($_SERVER['HTTP_HOST'] === '127.0.0.1') || //from localhost
            ($_SERVER['HTTP_HOST'] === '10.0.2.2') //from android emulator
    ) {
        $user = "root";
        $pass = "";
        $db = "center_test";
    }
}

$base_url = 'http://localhost/';
if (isset($_SERVER['HTTP_HOST'])) {
    $base_url = isset($_SERVER['HTTPS']) && strtolower($_SERVER['HTTPS']) !== 'off' ? 'https' : 'http';
    $base_url .= '://' . $_SERVER['HTTP_HOST'];
    $base_url .= str_replace(basename($_SERVER['SCRIPT_NAME']), '', $_SERVER['SCRIPT_NAME']);
}
$base_path = str_replace(basename($_SERVER['SCRIPT_NAME']), '', $_SERVER['SCRIPT_NAME']);

date_default_timezone_set('UTC');

//////////////////////////////////////////////////////////////////////////////
if (!function_exists('escape_date')) {

    function escape_date($str) {
        $timestamp = strtotime($str);
        return date("Y-m-d H:i:s", $timestamp);
    }

}

if (!function_exists('utf8_header')) {

    function utf8_header($type = 'text/html') {
        header('Content-Type: ' . $type . '; charset=utf-8');
    }

}

// ---------------------------------------------------------------------------

if (!function_exists('server_var')) {

    function server_var($id) {
        return isset($_SERVER[$id]) ? $_SERVER[$id] : '';
    }

}

if (!function_exists('is_post')) {

    function is_post() {
        return server_var('REQUEST_METHOD') == 'POST';
    }

}

if (!function_exists('is_get')) {

    function is_get() {
        return server_var('REQUEST_METHOD') == 'GET';
    }

}

// ---------------------------------------------------------------------------
if (!function_exists('debug_log')) {

    function debug_log($msg) {
        $filepath = 'log-' . date('Y-m-d') . '.php';
        $message = (' - ' . date('Y-m-d H:i:s') . ' --> ' . $msg . "\n");

        if (!$fp = @fopen($filepath, FOPEN_WRITE_CREATE)) {
            return FALSE;
        }

        flock($fp, LOCK_EX);
        fwrite($fp, $message);
        flock($fp, LOCK_UN);
        fclose($fp);

        @chmod($filepath, FILE_WRITE_MODE);
    }

}

if (!function_exists('escape_str')) {

    function escape_str($str, $like = FALSE) {
        if (is_array($str)) {
            foreach ($str as $key => $val) {
                $str[$key] = escape_str($val, $like);
            }

            return $str;
        }

        if (function_exists('mysql_escape_string')) {
            $str = mysql_escape_string($str);
        } else {
            $str = addslashes($str);
        }

        // escape LIKE condition wildcards
        if ($like === TRUE) {
            $str = str_replace(array('%', '_'), array('\\%', '\\_'), $str);
        }

        return $str;
    }

}

if (!function_exists('html_escape')) {

    function html_escape($var) {
        if (is_array($var)) {
            return array_map('html_escape', $var);
        } else {
            return htmlspecialchars($var, ENT_QUOTES, CHARSET);
        }
    }

}