Passing value as hidden parameter to next page

Question

I am trying to send value from one page to another page in WordPress as i do not want to repeat logic to fetch that value in other page. I am not very proficient in WordPress/PHP, if i have to do that in Java, i will create a hidden field and pass that value to server side code and from there can again set it as a request parameter, not sure how to achieve that in WordPress with help of PHP.

I have a page and a link "see more" on right hand navigation panel,once user click link, he/she is being redirected to another page ,but I need to show information based on values from the parent page

User is being redirected based on some rewrite rule and i am picking few values from using get_query_var().

I can do that by adding that parameter as query parameter, but i do not want to change current URL being generated.

Here is more information about my use case:

Site on which i am working is related to travelling and i am showing destination recommendations on few pages on its right hand side bar, for the UI layout, i am not showing all recommendations but few say "10" and than i am giving a link saying "Check all recommendations".

When user land on certain page, i am fetching categories assigned to that post and it is possible to have multiple categories say

1. hill-station
2. adventure etc

So based on these categories, i am showing them recommendations, so when user click on the click i want to pass this category information to next page so as i can show them eligible destination list.

Is there any other way to pass value to new page except for setting value in session?

Answer 1

Simply use a $_POST variable to set the terms to the page that handle the recomendations and use an hook into pre_get_posts to set the query.

I write a function that output the link, and you can use it as a template tag.

Add this function in a plugin or in your functions.php

function more_recomentation_link() {
  if ( ! is_single() && ! is_page() ) return;
  $post = get_queried_object();
  $cats = wp_get_object_terms( $post->ID, 'category', array('fields' => 'ids') );
  if ( ! empty($cats) ) {
    // I don't know which is the url that handle the recomandation showing
    // so I use home_url() change it with rigth url
    echo '<form method="post" action='. home_url() . ' id="see-more-form" style="display:none">';
    foreach ( $cats as $cat ) {
      echo '<input type="hidden" name="cats[]" value="' . $cat. '" />';
    }
    echo '</form>';
  }
  echo "<a href='javascript:void(0)' onclick='document.getElementById(\"see-more-form\").submit();return false;'>" . __('See More') . "</a>";
}

function set_recomendations_query( $query ) {
  if ( ! is_admin() && is_main_query() && isset($_POST['cats']) && ! empty($_POST['cats']) ) {
    $tax_query = array(
      'taxonomy' => 'category',
      'field' => 'id',
      'terms' => $_POST['cats']
    );
    $query->set('tax_query', array($tax_query));
    $query->set('posts_per_page', -1);
  }
}
add_action('pre_get_posts', 'set_recomendations_query');

The in the template, even in sidebar, show the 'See More' link simply using

<p><?php more_recomentation_link(); ?></p>