function change_pass($user_accounts_file, $username, $oldpass, $newpass) {
    if(false === file_exists($user_accounts_file)) {
        trigger_error(
            sprintf(
                'Акаунта $user_accounts_file не съществува на определеното местоположение: %s ',
                $user_accounts_file
            ),
            E_USER_ERROR
        );
        return false;
    }
    foreach(file($user_accounts_file) as $entry) {
        list($entry_key, $entry_username, $entry_password) = array_map('trim', explode('|', $entry));
        if($entry_username === $username && $entry_password === $oldpass) {
            if ( $entry_username == $username ) {
                $entry_key = $entry_key;
                $entry_username = $username;
                $new_password = $newpass;

                return (bool)file_put_contents(
                    $user_accounts_file,
                    sprintf(
                        "%s|%s|%srn",
                        $entry_key,
                        $entry_username,
                        $new_password
                    ),
                    FILE_APPEND | LOCK_EX
                );
            } else {
                return false;
            }
        }
    }
    return false;
}

return (bool)file_put_contents(
                    $user_accounts_file,
                    sprintf(
                        "%s|%s|%srn",
                        $entry_key,
                        $entry_username,
                        $new_password
                    ),
                    FILE_APPEND | LOCK_EX
                );

ea55e673b8189b3140a1b2dc67a0fe605ca0e605|admin|admin
xa55de673b81e05ca0e631123131231212312130|moderator|moderator

ea55e673b8189b3140a1b2dc67a0fe605ca0e605|admin|admin123

ea55e673b8189b3140a1b2dc67a0fe605ca0e605|admin|admin123
xa55de673b81e05ca0e631123131231212312130|moderator|moderator