Conexion.php

<?php

$host=""; //rellenar
$port=""; //con datos
$user=""; //de conexion
$pass=""; //para
$db=""; //mysqli

if ($port != ""){
  $HostFull = $host . ":" . $port;
}
else
{
  $HostFull = $host;
}

$connection = @new mysqli($HostFull, $user, $pass, $db);
if($conection->connect_error){
    die("Error en la conexion : ".$connection->connect_errno."-".$connection->connect_error);
}

$connection->set_charset("utf-8"); //Para UTF-8

//$connection es la variable de mysqli