There are a few scripts available on net which allow you to change a linux user password from PHP. but all of them are very complex and hard to implement , so after some hours of work , I’ve written this PHP script 🙂 it is very simple , in order for this to work you need to allow your webserver to run sed command as root through sudoers , or allow your webserver to write on your /etc/shadow file.
$username='USERNAME';
$password='PASSWORD'; // New Password
$sed='/bin/sed'; //Path to sed command
$salt = substr($username, 0, 2);
$pass_crypt = crypt($password, $salt);
$pass_crypt=str_replace("/","\/",$pass_crypt);
system($sed." -i 's/".$username.":[a-zA-z0-9/$\.]*/".$username.":".$pass_crypt."/g' /etc/shadow",$retval);