$password="123456";

md5($password);

Use md5(); to encrypts password to make it more secure

Look at these two databases, it's the same person and same info, the first one we don't encrypt his password, but the second one we encrypted his password.

When you encryte "john856" using this code, you'll see the result
"ad65d5054042fda44ba3fdc97cee80c6"

This is not a random result, everytime you encrypt the same password you will get the same result.

$password="john856";
$encrypt_password=md5($password);

echo $encrypt_password;

This is an example Login with encrypted password, but don't forget to encrypt password and insert into database when your user sign up.

// username and password sent from form
$myusername=$_POST['myusername'];
$mypassword=$_POST['mypassword'];

// encrypt password
$encrypted_mypassword=md5($mypassword);

$sql="SELECT * FROM $tbl_name WHERE username='$myusername' and password='$encrypted_mypassword'";
$result=mysql_query($sql);

You can learn to create login system here