simple user authentication in php

simple user authentication in php

<?php include_once('db.php');   
// Using include_once(), we are including the file db.php By  including this file, we automatically get connected to the database.
?> 


<?php

	$fname=$_POST['fname']; // pass data of firstname field through "POST" method
	$lname=$_POST['lname']; // pass data of lastname field through "POST" method
	$email=$_POST['email']; // pass data of email field through "POST" method
	$pass=$_POST['pass']; // pass data of password field through "POST" method

	//"INSERT INTO sign_up (first_name,last_name,email,password) VALUES ('$fname','$lname','$email','$pass')"
	
	$sql="INSERT INTO sign_up (first_name,last_name,email,password) VALUES ('$fname','$lname','$email','$pass')";
	$sry=mysql_query($sql); // mysql query executed 
if(!$sry)
{
	echo 'Failed'.mysql_error();

      echo "<br /><a href='sign_up.html'>Sign up</a>";

}
else
{
	echo "You are Successfuly signed up !! ";
	 echo "<br /><a href='sign_in.html'>Sign in</a>";
}
?>