<?php

if(isset($_POST['envia'])){

$user = $_POST['user'];
$pass = $_POST['pass'];

$consulta = mysql_query("SELECT * FROM users WHERE user = '$user' AND pass = '$pass'");
$consultando = mysql_num_rows($consulta);

if($consultando == '1'){echo "rolf, esse usuário existe amigo!";}else{

echo "eçe osoario nau existi!";

  }
}


?>

<form id="form1" action="" method="post">

<input type="text" name="user" /><input type="text" name="pass" /><input type="submit" name="envia" value="Enviar" />

</form>