Wp query

Savita Soni, co-founder AmiWorks & chief-poet for WPoets
Twitter @savitas

Ways to fetch posts & related data

• query_posts()
• new WP_Query()
• get_posts()
• $wpdb global db object

How query_posts() looks

query_posts( $args );
while ( have_posts() ) :
the_post();
//the_title(), the_ID(), the_permalink() etc..
endwhile;

// Reset Query
wp_reset_query();

How WP_Query() looks
// The Query
$the_query = new WP_Query( $args );

// The Loop
while ( $the_query->have_posts() ) :
$the_query->the_post();
echo '<li>' . get_the_title() . '</li>';
endwhile;
wp_reset_postdata();

How get_posts() looks

<?php
global $post;
$args = array( 'numberposts' => 5, 'offset'=> 1, 'category' => 1 );
$myposts = get_posts( $args );
foreach( $myposts as $post ) :
setup_postdata($post); ?>
<li><a href="<?php the_permalink(); ?>">
<?php the_title(); ?></a></li>
<?php endforeach;
?>

So lets see something which we may not know...

Conditional tags

is_author()
is_home()
is_archive()

we know this as well and use them frequently…

But have you seen this?

$wp_query = new WP_Query( $args );
$wp_query->is_author()
$wp_query->is_home()
$wp_query->is_archive()

Yes every query object has its own methods

so we can do this as well

$my_query = new WP_Query( $args );
while( $my_query->have_posts() ):
$my_query->the_post();
if( $my_query->is_author()){
// do something for author
}
endwhile;

why we always needs to call

wp_reset_query()

with query_posts() or WP_Query()

because when we do this

query_posts( 'cat=5');
while ( have_posts() ) :
the_post();
//the_title(), the_ID(), the_permalink() etc..
endwhile;

We have altered the main query...

How?
global $wp_query; //this is the main query object
Do anyone know this?
$wp_the_query

So the real main query object $wp_the_query
and $wp_query is the live copy of $wp_the_query

it is something like

$wp_the_query = new WP_Query();
$wp_query = &$wp_the_query;

when we call query_posts(), it works like this

function query_posts($query) {
$GLOBALS['wp_query'] = new WP_Query();
return $GLOBALS['wp_query']->query($query);
}

and when we call wp_reset_query()

function wp_reset_query() {
$GLOBALS['wp_query'] = $GLOBALS['wp_the_query'];
}

how many query(s) get called when we call
WP_Query()?

Is it running only one query with your passed
arguments????

it is running 4 queries

1. Select SQL_CALC_FOUND_ROWS....FROM wp_posts
limit 0,10

2. Select FOUND_ROWS();

3. Get all metadata attached to these posts.

4. Get all terms for these posts.

off some arguments selectively

new WP_Query(
array(
'no_found_rows' => false,
'update_post_meta_cache' => false,
'update_post_term_cache' => false
)
)

what if I need to modify the main query only?

Use pre_get_posts hook

function exclude_category( $query ) {
$query->set( 'cat', '-1,-1347' );
}
add_action( 'pre_get_posts', 'exclude_category' );

Now problem with this...

it gets called for every post query
get_posts()
WP_Query()
query_posts()

what if I just need it for home page query?

now $wp_the_query object will help

global $wp_the_query;
if( $wp_the_query == $query
and $query->home()){
$query->set( 'cat', '-1,-1347' );
}
}
add_action( 'pre_get_posts', 'exclude_category' );

After WordPress 3.3 we have an awesome function

is_main_query()

So rather than writing

global $wp_the_query;
//if( $wp_the_query == $query and $query->home())
if( $query->is_main_query() and $query->home()) {
$query->set( 'cat', '-1,-1347' );
}

Conclusion

 Try to avoid using query_posts()
 If query_posts() is used then reset it with
wp_reset_query()
 Use pre_get_posts hook to alter main query &
use it with is_main_query() condition tag

Thanks

Email: savita@amiworks.com
Twitter: @savitas

Wp query

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