Hashing a password with Blowfish, then checking if the entered password matches.

blowfish_hash.php

<?php

/**
  * Hashing the password at the time of the registration
  */
// Call function to hash the registration password (then enter it into the database however you choose)
blow_hash($_POST['password'])

// Hash passwords with blowfish
function blow_hash($password) {
  return password_hash($password, PASSWORD_BCRYPT);
}

/**
  * Checking that the entered password matches what is in the database at login
  */

// Get the password the user entered from the login form
$entered_password = $_POST['password'];

// Run a query to check if the username is valid first, then get the existing password from the database and store it in a variable
$right_password = $user->password;

// Verify that the password stored in the $right_password variable from the database
// matches the password from the login form, stored as $entered_password
function verify_pass($entered_password, $right_password) {
  if(password_verify($entered_password, $right_password)) {
    return true;
  } else {
    return false;
  }
}

// Allow the user to login if the password is a match, or give erros if it is not
if(verify_pass($entered_password, $right_password)) {
  // set logged in session variable and send them on to the logged in landing page
} else {
  // return invalid login errors
}