passwordPHP5.5 password PHP library

<?php
/**
 * A Compatibility library with PHP 5.5's simplified password hashing API.
 *
 * @author Anthony Ferrara <ircmaxell@php.net>
 * @license http://www.opensource.org/licenses/mit-license.html MIT License
 * @copyright 2012 The Authors
 */
namespace {
    if (!defined('PASSWORD_BCRYPT')) {
        /**
         * PHPUnit Process isolation caches constants, but not function declarations.
         * So we need to check if the constants are defined separately from 
         * the functions to enable supporting process isolation in userland
         * code.
         */
        define('PASSWORD_BCRYPT', 1);
        define('PASSWORD_DEFAULT', PASSWORD_BCRYPT);
        define('PASSWORD_BCRYPT_DEFAULT_COST', 10);
    }

I believe that when many PHP developers first came into contact with PHP, the preferred encryption function for handling passwords might be MD5. This is what I did at the time:

$password = md5($_POST["password "]);

Does the above code sound familiar? However, the MD5 encryption method seems to be not very popular in the PHP world at present, because its encryption algorithm is a bit simple, and many password cracking sites store a lot of MD5 encrypted password strings, so here I strongly discourage using MD5 alone to encrypt user passwords.

SHA256 and SHA512

In fact, there is a SHA1 encryption method at the same time as the previous MD5, but the algorithm is relatively simple, so I will briefly mention it here. The SHA256 and SHA512 we are about to talk about here are encryption functions from the SHA2 family. You may have guessed it by looking at the names. These two encryption methods generate hash strings of 256 and 512 bit length respectively.