Add Field To Custom WP Login Form - wordpress

Question

I have a custom login form that I display on a page using the following:
$my_login_args = apply_filters( 'my_login_page_args', array(
'echo' => true,
'redirect' => site_url( $_SERVER['REQUEST_URI'] ),
'form_id' => 'my_login_form',
'label_username' => esc_html__( 'Email Address' ),
'label_password' => esc_html__( 'Password' ),
'label_remember' => esc_html__( 'Remember Me' ),
'label_log_in' => esc_html__( 'Sign In' ),
'id_username' => 'user_login',
'id_password' => 'user_pass',
'id_remember' => 'rememberme',
'id_submit' => 'wp-submit',
'remember' => true,
'value_username' => NULL,
'value_remember' => false
) );
wp_login_form( $my_login_args ); ?>
I need to pass a custom variable ($my_custom_id) stored in the login page through to the redirected page a user sees after login. Is there any way to append the URL with this variable using POST or GET or is the best solution to add this as a hidden field in the form?
Also, in terms of adding an extra field to the form I've tried adding a custom input box to the form using
add_action('login_form','my_added_login_field');
function my_added_login_field(){
//Output your HTML
?>
<p>
<label for="my_extra_field">My extra field<br>
<input type="text" tabindex="20" size="20" value="" class="input" id="my_extra_field" name="my_extra_field_name"></label>
</p>
<?php
}
However this only adds the field to the main Wordpress login and not my custom form. Any thoughts on how best to proceed?

Answer 1

You can you add custom field in login form at top, bottom, and in middle.
I have added login field in login_form_middle.
For Reference https://core.trac.wordpress.org/browser/tags/4.9/src/wp-includes/general-template.php#L390
https://codex.wordpress.org/Customizing_the_Login_Form
/*
You can use these hooks as well to place your fields
login_form_bottom - login_form_top - login_form_middle
*/
add_filter('login_form_middle','my_added_login_field');
function my_added_login_field(){
//Output your HTML
$additional_field = '<div class="login-custom-field-wrapper"">
<label for="my_extra_field">My extra field<br>
<input type="text" tabindex="20" size="20" value="" class="input" id="my_extra_field" name="my_extra_field_name"></label>
</div>';
return $additional_field;
}