Unable to save Query Vars with a post

I'm trying to save Query Vars to a post for later retrieval.

I'm using permalinks in this format: domain.com/%category%/%postname%/

Example:

I create a following page
```
domain.com/page-003/
```

I add Query Var called email to the page

add_query_arg('email', 'test@abc.com', 'domain.com/page-003/')

Now when I call

get_permalink($post_id);

I get

domain.com/page-003/

Instead of

domain.com/page-003/?email=test@abc.com

What am I missing? Aren't Query Vars saved with a post?

Solution

You want to save some meta data which you want to restore later on and add as query arg into the URL.

You need to first save it as post_meta like e.g. when you save post with that data. You use:

<?php update_post_meta(get_the_ID(), 'email_address', 'abc@mail.com'); ?>

More details: https://codex.wordpress.org/Function_Reference/update_post_meta

Then during the retrieval, you may hook into a HOOK early on like template_redirect or earlier of the post you can get post_meta to get the email and then add to query arg:

<?php $email = get_post_meta( get_the_ID(), 'email_address' ); ?>

Then

esc_url( add_query_arg( 'email', $email, get_permalink( get_the_ID() ) ) );

Something like that, code is untested, I just wrote here, you may please read detailed doc in codex for each function used above.

Update: How to update/fill Ninja form field from Meta Value:

add_filter( 'ninja_forms_render_default_value', 'wm_the_value' , 10 , 3);

function wm_the_value( $default_value, $field_type, $field_settings ) {
    if( 'textbox' == $field_type && in_array('ref' , $field_settings)){
        $default_value = get_post_meta(get_the_ID(),'_listing_mls', true);
    }

    return $default_value;
}

'ref' is field name in Ninja form. '_listing_mls' is meta_key name from WP database.

Hope it works for you.