How to change or convert MySQL to MySQLi

<?php
define ('hostnameorservername','localhost'); //Your server name or hostname goes in here
define ('serverusername','root'); //Your database username goes in here
define ('serverpassword',''/); //Your database password goes in here
define ('databasenamed','scmplus'); //Your database name goes in here

$mysqli = new mysqli( hostnameorservername, serverusername, serverpassword, databasenamed );

if ($mysqli->connect_errno)
{
printf("Connection failed: %s\n", $mysqli->connect_error);
exit();
}

if (!$mysqli->set_charset("utf8"))
{
printf("Error loading character set utf8: %s\n", $mysqli->error);
exit();
}

if ( !function_exists('mysql_connect') )
{
function mysql_connect( $sql_host, $sql_username, $sql_password )
{
$mysqli_connect = mysqli_connect( $sql_host, $sql_username, $sql_password );
return $mysqli_connect;
}
}

if ( !function_exists('mysql_select_db') )
{
function mysql_select_db( $database, $connection )
{
$mysqli_select_db = mysqli_select_db( $connection, $database );
return $mysqli_select_db;
}
}

if (!function_exists('mysql_real_escape_string'))
{
function mysql_real_escape_string($string)
{
global $mysqli;
if($string){
$real_escape_string = $mysqli->real_escape_string($string);
return $real_escape_string;
}
}
}

if (!function_exists('mysql_query'))
{
function mysql_query($query)
{
global $mysqli;
if($query) {
$result = $mysqli->query($query);
return $result;
}
}
}

if (!function_exists('mysql_fetch_array'))
{
function mysql_fetch_array($result){
if($result){
$row = $result->fetch_assoc();
return $row;
}
}
}

if (!function_exists('mysql_num_rows'))
{
function mysql_num_rows($result){
if($result){
$row_cnt = $result->num_rows;;
return $row_cnt;
}
}
}

if (!function_exists('mysql_free_result'))
{
function mysql_free_result($result)
{
if($result){
global $mysqli;
$result->free();
}
}
}

if (!function_exists('mysql_data_seek'))
{
function mysql_data_seek($result, $offset){
if($result){
global $mysqli;
return $result->data_seek($offset);
}
}
}

if (!function_exists('mysql_close'))
{
function mysql_close(){
global $mysqli;
return $mysqli->close();
}
}
if (!function_exists('mysql_insert_id'))
{
function mysql_insert_id(){
global $mysqli;
$lastInsertId = $mysqli->insert_id;
return $lastInsertId;
}
}

if (!function_exists('mysql_error'))
{
function mysql_error(){
global $mysqli;
$error = $mysqli->error;
return $error;
}
}
?>