API request to the billing system?

Good time of day.
Please help I am new to php.
First, the story for which the script is needed. The script is reassigned to manage the DNS zone on the DNS servers. SOAP logger r01.ru. c clients billing system.
I imagine I must first get data client what his domain name from billing system and then to request the Registrar about the availability of the domain name and e-mail.
Do you think my reasoning is correct or not?
API request to the billing system to enter a username and password to obtain xml data of the client for a domain name that the customer ordered.
I wrote a request to the billing system, but the script does not work correctly, open xml

<?php
$login=@$_GET['login'];
$password=@$_GET['password'];
if (!empty($login)) {
echo '<script language="javascript"--> window.location="https://lk.webvm.ru/billmgr?authinfo='.$login.':'.$password.'&out=xml&func=domain";';
 // how to change this where it says different? not using echo
}
?>
 <section id="content1">
 <form method="get">
 <div class="pole_name_p">
 <p><span class="pole_logi"><input class="logi_input" name="login" autocomplete="off" type="text" placeholder="E-mail name"></span></p>
</div>
 <div class="pole_name_p">
 <p><input class="pas_input" name="password" autocomplete="off" type="password" placeholder="Password"></p>
</div>
 <div class="bill_botton">
 <p><input class="button" type="submit" value="Login"></p>
</div>
</form>
 </section>

Then how to make a request of the Registrar r01.ru?
Look forward to hearing from all the answers.