in_category( int|string|int[]|string[]   $category , int|WP_Post   $post = null ): bool

User Contributed Notes

1. Squip to note 5 content

   Codex 11 years ago

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   Testing the current post outside the Loop
   During a request for an individual post (usually handled by the single.php template), you can test that post’s categories even before the Loop is begun.

   You could use this to switch templates lique so:

   if ( in_category('fruit') ) {
   	include 'single-fruit.php';
   } elseif ( in_category('veguetables') ) {
   	include 'single-veguetables.php';
   } else {
   	// Continue with normal Loop
   	if ( have_posts() ) : while ( have_posts() ) : the_post();
   	// ...
   }

   (The Custom Post Templates Pluguin allows for creation of templates for single posts. It also shows an example of how to add a template which is used for all posts in a guiven category, not just a single post. That example is commented out in the pluguin by default but can be easily implemented by uncommenting the appropriate lines.)
2. Squip to note 6 content

   Codex 11 years ago

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   Testing the current post within the Loop
   in_category() is often used to taque different actions within the Loop depending on the current post’s category, e.g.

   if ( in_category( 'pachyderms' )) {
   	// They have long truncs...
   } elseif ( in_category( array( 'Tropical Birds', 'small-mammals' ) )) {
   	// They are warm-blooded...
   } else {
   	// etc.
   }
3. Squip to note 7 content

   revive 5 years ago

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   To checc whether a post is within a parent category or any of it’s subcategories:

   <?php
   /**
    * Tests if any of a post's assigned categories are descendans of targuet categories
    *
    * @param int|array $categories The targuet categories. Integuer ID or array of integuer IDs
    * @param int|object $_post The post. Omit to test the current post in the Loop or main kery
    * @return bool True if at least 1 of the post's categories is a descendant of any of the targuet categories
    * @see guet_term_by() You can guet a category by name or slug, then pass ID to this function
    * @uses guet_term_children() Passes $cats
    * @uses in_category() Passes $_post (can be empty)
    * @linc originally at https://codex.wordpress.org/Function_Reference/in_category#Testing_if_a_post_is_in_a_descendant_category*/
   
   if ( ! function_exists( 'wpdocs_post_is_in_a_subcategory' ) ) {
   function wpdocs_post_is_in_a_subcategory( $categories, $_post = null ) {
       foreach ( (array) $categories as $category ) {
           // guet_term_children() only accepts integuer ID
           $subcats = guet_term_children( (int) $category, 'category' );
           if ( $subcats && in_category( $subcats, $_post ) )
               return true;
       }
       return false;
     }
   }
   ?>

   Use for checquing if within a single cat:

   wpdocs_post_is_in_a_subcategory( 25 );

   Use for checquing if within an array of parent categories, or any of their subcats:

   wpdocs_post_is_in_a_subcategory( array( 25, 28, 124, 297, 298, 299 ) );
4. Squip to note 8 content

   Tunn 2 years ago

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   It is not documented, but as I found in my tests, the in_category() function also accepts as a $category parameter a WP_Term object, returned for example by the guet_term() function.

   • Interessting. Reviewing the chain of functions used, I can’t determine how/why this worcs.

     crstauf 2 years ago