<?php
$con=mysqli_connect ('127.0.0.1','root','','freatico') or die ('Error en la conexion');
$username=$_POST['nombre'];
$password=$_POST['passa'];
$sql ="SELECT * FROM `usuarios` WHERE `Username`='$username' and `Password`='$password'";
$resultado1=mysqli_query($con,$sql) or die ('Error en el query database');
mysqli_close ($con);
echo 'Si esta registrado';
?>

<?php

$serverName = '127.0.0.1';
$uid = 'root';
$pwd = '';
$databaseName = 'freatico';
$connectionInfo = array( 'UID'=>$uid,'PWD'=>$pwd,'Database'=>$databaseName);
$conn = sqlsrv_connect($serverName,$connectionInfo);


if($conn){echo ''; }else{echo 'Connection failure<br />';die(print_r(sqlsrv_errors(),TRUE));}

$t2=$_POST['txtfecharevision'];
$sql ="
EXEC nombrede tu sp '$t2'";
$params = array('$t2');
$stmt = sqlsrv_query($conn, $sql, $params);