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is_main_query()

Determines whether the query is the main query.

Description

For more information on this and similar theme functions, check out the Conditional Tags article in the Theme Developer Handbook.

Return

(bool) Whether the query is the main query.

More Information

The is_main_query() function is a conditional function that can be used to evaluate whether the current query (such as within the loop) is the “main” query (as opposed to a secondary query).

This function is most commonly used within hooks to distinguish WordPress’ main query (for a page, post, or archive) from a custom/secondary query.

is_main_query() may be used with both front-end queries (theme templates, plugins, etc.), as well as admin queries. It will return true if the current query is the main query, and false if not.

Usage 


if ( is_main_query() ) {
// do stuff
}

Under the Hood

This function does not accept any parameters. Instead, it automatically compares the $wp_query object (i.e., the “current query”) with the $wp_the_query object (the “main query”)

This function is an alias for the method WP_Query::is_main_query(). In filter or action hook callbacks that are passed the WP_Query object, such as ‘pre_get_posts‘, it is circular to call this function. Instead, directly call the passed object’s method. For example, if your filter callback assigns the passed WP_Query object to $query, you would call the method like so:
$query->is_main_query()

Example 

add_action( 'pre_get_posts', 'foo_modify_query_exclude_category' );
function foo_modify_query_exclude_category( $query ) {
    if ( ! is_admin() && $query->is_main_query() && ! $query->get( 'cat' ) )
        $query->set( 'cat', '-5' );
}

Source

File: wp-includes/query.php 

function is_main_query() {
	if ( 'pre_get_posts' === current_filter() ) {
		$message = sprintf(
			/* translators: 1: pre_get_posts, 2: WP_Query->is_main_query(), 3: is_main_query(), 4: Link to codex is_main_query() page. */
			__( 'In %1$s, use the %2$s method, not the %3$s function. See %4$s.' ),
			'<code>pre_get_posts</code>',
			'<code>WP_Query->is_main_query()</code>',
			'<code>is_main_query()</code>',
			__( 'https://codex.wordpress.org/Function_Reference/is_main_query' )
		);
		_doing_it_wrong( __FUNCTION__, $message, '3.7.0' );
	}

	global $wp_query;
	return $wp_query->is_main_query();
}

Uses

Uses Description
wp-includes/l10n.php: __()

Retrieve the translation of $text.
wp-includes/class-wp-query.php: WP_Query::is_main_query()

Is the query the main query?
wp-includes/functions.php: _doing_it_wrong()

Mark something as being incorrectly called.
wp-includes/plugin.php: current_filter()

Retrieve the name of the current filter or action.

Changelog

Version Description
3.3.0 Introduced.

© 2003–2019 WordPress Foundation
Licensed under the GNU GPLv2+ License.
https://developer.wordpress.org/reference/functions/is_main_query