Ilexiste des scénarios légitimes d'utilisation de query_posts($query),parexemple:

1. Vous souhaitez afficher une liste d'articles ou d'articles detype articlepersonnalisé sur unepage (à l'aide d'unmodèle depage)

2. Vous souhaitez que lapagination de cesmessagesfonctionne

Maintenant,pourquoi voudriez-vous l'afficher sur unepage au lieu d'utiliser unmodèle d'archive?

1. C'estplusintuitifpour un administrateur (votre client?) -ilpeut voir lapage dans les "Pages"

2. Ilestpréférable de l'ajouter auxmenus (sans lapage,ils devraient ajouter directement l'url)

3. Si vous souhaitez afficher du contenu supplémentaire (texte,vignette depublication outout autreméta-contenupersonnalisé) sur lemodèle,vouspouvezfacilement l'obtenir àpartir de lapage (ettout cela a égalementplus de senspour le client). Voyez si vous avez utilisé unmodèle d'archive,vous devez soit coderen dur le contenu supplémentaire,soit utiliserparexemple des options dethème/plugin (ce qui le rendmoinsintuitifpour le client)

Voici unexemple de code simplifié (qui serait sur votremodèle depage -parexemple,page-page-of-posts.php):

 /**
 * Template Name: Page of Posts
 */

while(have_posts()) { // original main loop - page content
  the_post();
  the_title(); // title of the page
  the_content(); // content of the page
  // etc...
}

// now we display list of our custom-post-type posts

// first obtain pagination parametres
$paged = 1;
if(get_query_var('paged')) {
  $paged = get_query_var('paged');
} elseif(get_query_var('page')) {
  $paged = get_query_var('page');
}

// query posts and replace the main query (page) with this one (so the pagination works)
query_posts(array('post_type' => 'my_post_type', 'post_status' => 'publish', 'paged' => $paged));

// pagination
next_posts_link();
previous_posts_link();

// loop
while(have_posts()) {
  the_post();
  the_title(); // your custom-post-type post's title
  the_content(); // // your custom-post-type post's content
}

wp_reset_query(); // sets the main query (global $wp_query) to the original page query (it obtains it from global $wp_the_query variable) and resets the post data

// So, now we can display the page-related content again (if we wish so)
while(have_posts()) { // original main loop - page content
  the_post();
  the_title(); // title of the page
  the_content(); // content of the page
  // etc...
}
 

Maintenant,pour êtreparfaitement clair,nouspourrions éviter d'utiliser query_posts()ici aussiet utiliser WP_Query à laplace - comme ceci:

 // ...

global $wp_query;
$wp_query = new WP_Query(array('your query vars here')); // sets the new custom query as a main query

// your custom-post-type loop here

wp_reset_query();

// ...
 

Maispourquoiferions-nous cela alors quenous avons une sijoliepetite fonction disponible?

There are legitimate scenarios for using query_posts($query), for example:

1. You want to display a list of posts or custom-post-type posts on a page (using a page template)

2. You want to make pagination of those posts work

Now why would you want to display it on a page instead of using an archive template?

1. It's more intuitive for an administrator (your customer?) - they can see the page in the 'Pages'

2. It's better for adding it to menus (without the page, they'd have to add the url directly)

3. If you want to display additional content (text, post thumbnail, or any custom meta content) on the template, you can easily get it from the page (and it all makes more sense for the customer too). See if you used an archive template, you'd either need to hardcode the additional content or use for example theme/plugin options (which makes it less intuitive for the customer)

Here's a simplified example code (which would be on your page template - e.g. page-page-of-posts.php):

/**
 * Template Name: Page of Posts
 */

while(have_posts()) { // original main loop - page content
  the_post();
  the_title(); // title of the page
  the_content(); // content of the page
  // etc...
}

// now we display list of our custom-post-type posts

// first obtain pagination parametres
$paged = 1;
if(get_query_var('paged')) {
  $paged = get_query_var('paged');
} elseif(get_query_var('page')) {
  $paged = get_query_var('page');
}

// query posts and replace the main query (page) with this one (so the pagination works)
query_posts(array('post_type' => 'my_post_type', 'post_status' => 'publish', 'paged' => $paged));

// pagination
next_posts_link();
previous_posts_link();

// loop
while(have_posts()) {
  the_post();
  the_title(); // your custom-post-type post's title
  the_content(); // // your custom-post-type post's content
}

wp_reset_query(); // sets the main query (global $wp_query) to the original page query (it obtains it from global $wp_the_query variable) and resets the post data

// So, now we can display the page-related content again (if we wish so)
while(have_posts()) { // original main loop - page content
  the_post();
  the_title(); // title of the page
  the_content(); // content of the page
  // etc...
}

Now, to be perfectly clear, we could avoid using query_posts() here too and use WP_Query instead - like so:

// ...

global $wp_query;
$wp_query = new WP_Query(array('your query vars here')); // sets the new custom query as a main query

// your custom-post-type loop here

wp_reset_query();

// ...

But, why would we do that when we have such a nice little function available for it?

Jemodifie la requête WordPress defunctions.php:

 //unfortunately, "IS_PAGE" condition doesn't work in pre_get_posts (it's WORDPRESS behaviour)
//so you can use `add_filter('posts_where', ....);`    OR   modify  "PAGE" query directly into template file

add_action( 'pre_get_posts', 'myFunction' );
function myFunction($query) {
    if ( ! is_admin() && $query->is_main_query() )  {
        if (  $query->is_category ) {
            $query->set( 'post_type', array( 'post', 'page', 'my_postType' ) );
            add_filter( 'posts_where' , 'MyFilterFunction_1' ) && $GLOBALS['call_ok']=1; 
        }
    }
}
function MyFilterFunction_1($where) {
   return (empty($GLOBALS['call_ok']) || !($GLOBALS['call_ok']=false)  ? $where :  $where . " AND ({$GLOBALS['wpdb']->posts}.post_name NOT LIKE 'Journal%')"; 
}
 

I modify WordPress query from functions.php:

//unfortunately, "IS_PAGE" condition doesn't work in pre_get_posts (it's WORDPRESS behaviour)
//so you can use `add_filter('posts_where', ....);`    OR   modify  "PAGE" query directly into template file

add_action( 'pre_get_posts', 'myFunction' );
function myFunction($query) {
    if ( ! is_admin() && $query->is_main_query() )  {
        if (  $query->is_category ) {
            $query->set( 'post_type', array( 'post', 'page', 'my_postType' ) );
            add_filter( 'posts_where' , 'MyFilterFunction_1' ) && $GLOBALS['call_ok']=1; 
        }
    }
}
function MyFilterFunction_1($where) {
   return (empty($GLOBALS['call_ok']) || !($GLOBALS['call_ok']=false)  ? $where :  $where . " AND ({$GLOBALS['wpdb']->posts}.post_name NOT LIKE 'Journal%')"; 
}

Justepour souligner quelques améliorations à la réponse acceptéepuisque WordPress a évolué aufil dutempset que certaines choses sont différentesmaintenant (cinq ansplustard):

pre_get_postsest unfiltre,pourmodifiern'importe quelle requête. Ilest leplus souvent utilisépourmodifier uniquement la «requêteprincipale»:

C'esten fait un crochet d'action. Pas unfiltre,et cela affecteran'importe quelle requête.

La requêteprincipale apparaît dans vosmodèles sous laforme:

 if( have_posts() ):
    while( have_posts() ): the_post();
       //The loop
    endwhile;
endif;
 

Enfait,cen'estpas vrainonplus. Lafonction have_postsitère l'objet global $wp_query quin'estpas lié uniquement à la requêteprincipale. global $wp_query;peut également êtremodifié avec les requêtes secondaires.

 function have_posts() {
    global $wp_query;
    return $wp_query->have_posts();
}
 

get_posts ()

Il s'agitessentiellement d'un wrapperpour uneinstance distincte d'un objet WP_Query.

Enfait,denosjours WP_Queryest une classe,nous avons donc uneinstance d'une classe.

Pour conclure: aumoment où @StephenHarris a écrit,tout cela étaitprobablement vrai,mais aufil dutemps,les choses dans WordPress ont changé.

Just to outline some improvements to the accepted answer since WordPress evolved over the time and some things are different now (five years later):

pre_get_posts is a filter, for altering any query. It is most often used to alter only the 'main query':

Actually is an action hook. Not a filter, and it will affect any query.

The main query appears in your templates as:

if( have_posts() ):
    while( have_posts() ): the_post();
       //The loop
    endwhile;
endif;

Actually, this is also not true. The function have_posts iterates the global $wp_query object that is not related only to the main query. global $wp_query; may be altered with the secondary queries also.

function have_posts() {
    global $wp_query;
    return $wp_query->have_posts();
}

get_posts()

This is essentially a wrapper for a separate instance of a WP_Query object.

Actually, nowadays WP_Query is a class, so we have an instance of a class.

To conclude: At the time @StephenHarris wrote most likely all this was true, but over the time things in WordPress have been changed.