Php Array Field Logic Issue

So, I have code directly below for setting up inset array. Problem is with user_admin. I have a piece of a form I am not calling if their profile is being edited by themselves (as to not allow last admin to be removed from site) If I allow input to be called, everything works fine. If it is not called (while wrapped in if statement) and form is submitted, it always reverts user_admin to 0 (removes admin ability)

$data = array(
            'user_id'      => $_GET['user'],
            'user_company' => $_POST['user_company'],
            'user_role'    => $_POST['user_role'],
            'user_admin'   => (($_POST['user_admin']  || $_GET['user_admin']) == '1') ? '1': '0',
        );

and the part of the form

<?php // if (get_current_user_id() != $_GET['user']) : ?>
                <div class="row"> 
                    <div class="col-xs-12">
                        <label>Member's Site Capabilities<span class="flaticon-questions1" data-toggle="tooltip" data-placement="top" title="Administrator allows changes to project settings and invitation/deletion of team members. It is recommended to have at least one architect administrator and one contractor administrator."></label> 
                    </div>
                    <div class="col-xs-12">
                        <select name="user_admin" required>
                            <option value="0"<?php selected('0', $user->admin); ?>>Standard</option>
                            <option value="1"<?php selected('1', $user->admin); ?>>Site Administrator</option>
                        </select>
                    </div>
                </div>
            <?php // endif; ?>

Any suggestions on getting the admin to stick if its already set to something. I could hidden field it but don’t want to make it reachable.
Apologize if this is trivial, a bit of a neophyte here.

Thank you.