How to change or convert MySQL to MySQLi

CODE

<?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','chat'); 				//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;
	}
}
?>