User Validation/Authentication in PHP

If a user visits a website, where he is asked for validating his username and password and will be validated with the MySQL Database. the following scripts demonstrate this.
Step 1: create a database called dummy by executing “create database dummy” in mysql command window or shell window
Step 2: Create a table called usertable with two fields ‘user’ and ‘pass’ and populate with some values.
create table usertable (user varchar(20), pass varchar(30));
insert into usertable values (’pradeep’,'pradeep’);

Step 3: write the following html script and name it as user.html
<form method=post action=user.php>
Enter the Username: <input type=text name=username> <BR>
Enter the password: <input type=password name=password> <BR>
<input type=submit>
</form>
Step 4: Write the following PHP script and name it as user.php
<?php
$user=$_POST['username']; //get the username from the previous page (html page)
$pass=$_POST['password']; //get the password from the previous page
$conn=mysql_connect(”localhost”,”root”,”abc123”) or die(”Connection Failed”. mysql_error());
mysql_select_db(”dummy”,$conn) or die(mysql_error());
$query=”Select * from usertable where user=’$user’ and pass=md5(’$pass’)”;
$result=mysql_query($query) or die(mysql_error());
$num = mysql_num_rows($result);//returns atleast 1 row if the username password combination is valid
echo $num;//display the number of rows returned
if($num != 0)
{
echo “Welcome Mr.$user, you are authenticated”;
}
else
{
echo “Username/password combination Failed”;
}
mysql_close($conn);
?>
The above script checks for the username and password combination, if the combination is success, then atleast one row will be returned, else the returned rows will be 0.