<?php
//error_reporting(E_ALL); ini_set('display_errors', 1);

// input from user
$input_username = "michael";
$input_password = "password";

// user retrieved from db
$user = retrieve_user($input_username);

// if user's exists, verify the password
if ($user) {

    $db_hash = $user['password'];

    // combine username and password of the user
    $input = urlencode("$input_username:$input_password");

    // verify user's input
    if (password_verify($input, $db_hash)) {
        echo "password verified";
    } else {
        echo "password incorrect";
    }
} else {
    echo "username or password invalid";
}

/**
 * Retrieve user from database
 */
function retrieve_user($username)
{
    // ... get user's record by his username
    // SELECT id, username, password FROM user WHERE username = $username

    // this is generated when user is created
    $hash = password_hash(urlencode("michael:password"), PASSWORD_DEFAULT);

    // sample of user's record
    $user = [
        'id' => 1,
        'username' => 'adam',
        'password' => $hash,
    ];

    return $user;
}