WHMCS Registration form for mobile

[mo80]

Dear,

Hope every one is fine and I am new here and Want to solve my queries.

API: https://developers.whmcs.com/api-reference/addclient/

I have one question, I want to create a register form in which all below fields are hard bind like share below:

            'companyname' => 'Company Name LLC',
            'address1' => 'Company Address',
            'city' => 'Company City',
            'state' => 'Delaware',
            'postcode' => '000000',
            'country' => 'US',
            'phonenumber' => '302-000-0000',
            'skipvalidation' => 'bool',
            'responsetype' => 'json',

So user need to provide the below details only:

'tax_id' => 'string',
'clientip' => 'string',
'password2' => 'password',
 'email' => 'string',           
'firstname' => 'string',
'lastname' => 'string',

then he press the submit button of api link so all string and password variable get filled by customer information which he is providing on the registration form

Through this customer will see only 6 options in registration form.

Note: This form is use on mobile site so for me its must to use api so please give me solution on above query.

I think that its need to be work like this (Correct me if i am wrong); https://domainname/testapi.php?lastname=$string?=tax-id=$string or any way just help me on this.

I just want that my form get these 

'tax_id' => 'string', 'clientip' => 'string', 'password2' => 'password', 'email' => 'string', 'firstname' => 'string', 'lastname' => 'string',

from user easily and then he press the submit button and user get registered

Thank You