login system

[alex57]

I am trying to create a login system. The values in the password and username textboxes are checked against my database and if they are in there access is granted. However, when the page loads the condition is automatically checked with blank values and so access is denied. Is there a way of preventing the page from automatically using these blank values upon loading??

thanks

My code is below

<?php
$username = $_REQUEST['username'];
$password = $_REQUEST['password'];

mysql_connect("localhost", "root", "dinosaur") or die(mysql_error());

mysql_select_db("info") or die(mysql_error());



$result = mysql_query("SELECT * FROM users WHERE username = '$username' && password='$password'");

$row = mysql_fetch_array($result);//the result

if(($row['username'] == $username) && ($row['password'] == $password) && (mysql_numrows($result) == 1))//check username and password

{




?><div border = 1 color="red" align=middle>

You have have successfully logged in. You will be redirected shortly ...
</div>
<meta http-equiv="refresh" content="2; URL=home.php">
<?php


}
elseif (mysql_numrows($result) == 0) {

echo "incorrect login"; //shows when page loads because no results returned for the blank text boxes
}


?>

[Mwnciau]

<?php
if (!empty($_POST['password']) && !empty($_POST['username'])){
$username = $_POST['username'];
$password = $_POST['password'];

mysql_connect("localhost", "root", "dinosaur") or die(mysql_error());

mysql_select_db("info") or die(mysql_error());



$result = mysql_query("SELECT * FROM users WHERE username = '$username' && password='$password'");

$row = mysql_fetch_array($result);//the result

if(($row['username'] == $username) && ($row['password'] == $password) && (mysql_numrows($result) == 1))//check username and password

{




?><div border = 1 color="red" align=middle>

You have have successfully logged in. You will be redirected shortly ...
</div>
<meta http-equiv="refresh" content="2; URL=home.php">
<?php


}
elseif (mysql_numrows($result) == 0) {

echo "incorrect login"; //shows when page loads because no results returned for the blank text boxes
}
}
?>