is_category() WP 1.5.0

Conditional tag. Checks whether the category page is displayed or not.

It is a Boolean function, i.e. this function returns a true if the condition matches and false if not.

If the $category parameter is specified, this function will additionally check if the query is for one of the categories specified.

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

No Hooks.

Return

true/false.

Usage

if( is_category( $category ) ){
	// code...
}

$category(string/number/array)

Category ID, name, slug, or array of Category IDs, names, and slugs.
Default: ''

Examples

#1 An example of different types of checks

is_category();
// the function returns true if any category page is displayed.

is_category( '9' );
is_category( 9 );
// true if the category page with ID 9 is displayed.

is_category( 'Out there' );
// true if the category with the name 'Out there'.

is_category( 'out-there' );
// true if a category named 'out-there' is shown.

is_category( array( 9, 'blue-cheese', 'Stinky Cheeses' ) );
// Returns true if the category with ID 9 is shown or with name  
// 'blue-cheese', or with slug 'Stinky Cheeses'.

Code of is category: wp-includes/query.php ^{VER 5.1.1}

<?php
function is_category( $category = '' ) {
	global $wp_query;

	if ( ! isset( $wp_query ) ) {
		_doing_it_wrong( __FUNCTION__, __( 'Conditional query tags do not work before the query is run. Before then, they always return false.' ), '3.1.0' );
		return false;
	}

	return $wp_query->is_category( $category );
}

Related Functions

From tag: Conditional tags (page type and request)

More from tag: Conditional tags (all)

More from category: Queries

More from Template Tags: Main Functions