<?php
$id = "test";
$password = "test";
$sal = substr($id, 0, 2);
$password_crypted = crypt($password, $sal);
?>

.htpasswd 例）Id:test Pw:test

test:teH0wLIpW0gyQ

.htaccess

AuthUserFile (.htpasswdまでの絶対パス)
AuthGroupFile /dev/null
AuthName "Please enter your ID and password"
AuthType Basic
<LIMIT POST GET PUT>
require valid-user
</LIMIT>