将MD5更改为sha256或AES-256 SHA

Question

有人可以教我如何将MD5更改为sha256或AES 256 SHA，现在我在注册处理程序和登录处理程序中使用md5加密，那么我该如何更改代码呢？我改变它有什么不利之处吗？

register_handler.php

$password = ""; //password

//Password
$password = strip_tags($_POST['reg_password']); //Remove html tags
$password2 = strip_tags($_POST['reg_password2']); //Remove html tags

if(empty($error_array)) {
    $password = md5($password); //Encrypt password before sending to database

这是我的login_handler.php

<?php

 if(isset($_POST['login_button'])){
 $email = filter_var($_POST['log_email'], FILTER_SANITIZE_EMAIL);

 $_SESSION['log_email'] = $email; //Store email into session variable 
$password = md5($_POST['log_password']); //Get password