Title: Same query_vars, but different SQL request between main loop and Wp_Query
Last modified: August 21, 2016

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# Same query_vars, but different SQL request between main loop and Wp_Query

 *  Resolved [filchos](https://wordpress.org/support/users/filchos/)
 * (@filchos)
 * [12 years ago](https://wordpress.org/support/topic/same-query_vars-but-different-sql-request-between-main-loop-and-wp_query/)
 * Hello,
 * while writing a high level interface to WordPress for usage in the templates 
   I ran across a strange problem: Consider the following file `page.php`:
 *     ```
       <?php
   
       global $wp_query;
   
       $current = $wp_query;
       var_dump($current->request);
   
       $new = new WP_Query($wp_query->query_vars);
       var_dump($new->request);
   
       var_dump(array_diff_assoc($current->query_vars, $new->query_vars));
       ```
   
 * When I open a single page, say with id `5` and slug `foobar`, I’ll get the same
   query vars (tested with array_diff_assoc, as well as manually), but two different
   SQL requests:
 *     ```
       // $current:
       string 'SELECT   wps13t_posts.* FROM wps13t_posts  WHERE 1=1  AND (wps13t_posts.ID = '5') AND wps13t_posts.post_type = 'page'  ORDER BY wps13t_posts.post_date DESC '
   
       // $new:
   
       string 'SELECT   wps13t_posts.* FROM wps13t_posts  WHERE 1=1  AND wps13t_posts.post_name = 'foobar' AND wps13t_posts.post_type = 'post'  ORDER BY wps13t_posts.post_date DESC '
       ```
   
 * The first SQL request uses the page id (correct) and post_type _post_ (correct).
   The 2nd SQL request uses the post_name (correct, too) and post_type _page_ (error!).
 * I’m wondering why this strange behaviour occurs and whether it’s me or WordPress
   itself causing this error.
 * How can I init a WP_Query that acts the same as the default query?
 * Thanks for your help,
    /Olaf

Viewing 4 replies - 1 through 4 (of 4 total)

 *  Moderator [bcworkz](https://wordpress.org/support/users/bcworkz/)
 * (@bcworkz)
 * [12 years ago](https://wordpress.org/support/topic/same-query_vars-but-different-sql-request-between-main-loop-and-wp_query/#post-4952072)
 * It’s improper to directly pass query vars as WP_Query construction arguments.
   While there is a great deal of similarity between the two, some translation is
   applied so that the resulting request can often be different.
 * For example, for the main query, when the queried object is determined by the
   page slug (from getting a page by permalink), it causes the post type to be specified
   as ‘page’ in the request. But when you pass `'post_type'=>""` (from query vars)
   to a new WP_Query instance, the default ‘post’ value is assumed in the resulting
   request.
 *  Thread Starter [filchos](https://wordpress.org/support/users/filchos/)
 * (@filchos)
 * [12 years ago](https://wordpress.org/support/topic/same-query_vars-but-different-sql-request-between-main-loop-and-wp_query/#post-4952082)
 * Thank you for your help, bcworkz!
 * Sometimes WordPress is hard to understand since it’s kind of quaint sometimes.
 * Just one case:
 * `query_vars` of the current main loop contain both `name` and `pagename` without
   any problem in the main loop.
 * If I set these vars in the constructor of an own request I would expect the same
   result. But `post_type` will be set to `post` instead. Only when I remove the`
   name` var it works as excepted. I had similar cases with the vars `p` and `page_id`
   causing the same problem.
 * What I don’t understand: The main loop uses a `Wp_Query` instance as well (the
   global `wp_query`), but when I try to mimic the behaviour by constructing a Wp_Query
   instance that looks alike to me I get a different behaviour. Somehow the main
   loop must have another initialisation process as my code, but I didn’t find a
   clue, neither in the WordPress documentation, nor by checking the code itself.
 * There are heaps of loop and Wp_Query related functions and methods initialising,
   setting up, building objects, destroy object, reset the pointer and so one but
   I didn’t come up to a working combination.
 *  Moderator [bcworkz](https://wordpress.org/support/users/bcworkz/)
 * (@bcworkz)
 * [12 years ago](https://wordpress.org/support/topic/same-query_vars-but-different-sql-request-between-main-loop-and-wp_query/#post-4952129)
 * “kind of quaint” 😀 That’s a very judicious way of putting it!
 * While the main query does use an instance of WP_Query, it is not used in the 
   way you think. The main query’s query vars are from `WP::query_vars` which are
   established by `WP::parse_request()`. The `WP_Query::query_vars` you are using
   are really just a side effect for the main query. Note the two different classes
   here, WP and WP_Query, the distinction is important.
 * When you instantiate your own WP_Query object, the `WP_Query::query_vars` are
   quite important, they are established from the passed arguments with `WP_Query::
   parse_query()`, which is similar but different from the `WP::parse_request()`
   used by the main query. This is how ‘page’ gets worked into one request but not
   the other.
 *  Thread Starter [filchos](https://wordpress.org/support/users/filchos/)
 * (@filchos)
 * [12 years ago](https://wordpress.org/support/topic/same-query_vars-but-different-sql-request-between-main-loop-and-wp_query/#post-4952142)
 * Thank you for your explanations, bcworkz!
 * Now I understand better twice: How it works and how awkward WordPress’ internals
   are.

Viewing 4 replies - 1 through 4 (of 4 total)

The topic ‘Same query_vars, but different SQL request between main loop and Wp_Query’
is closed to new replies.

 * In: [Hacks](https://wordpress.org/support/forum/plugins-and-hacks/hacks/)
 * 4 replies
 * 2 participants
 * Last reply from: [filchos](https://wordpress.org/support/users/filchos/)
 * Last activity: [12 years ago](https://wordpress.org/support/topic/same-query_vars-but-different-sql-request-between-main-loop-and-wp_query/#post-4952142)
 * Status: resolved

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