This function has been deprecated. Use get_the_category() instead.

the_category_ID( bool $display = true )

Returns or prints a category ID.

Description

See also

Parameters

$display

(Optional) Whether to display the output.

Default value: true

Return

(int) Category ID.

Source

File: wp-includes/deprecated.php 

function the_category_ID($echo = true) {
	_deprecated_function( __FUNCTION__, 'WP-0.71', 'get_the_category()' );

	// Grab the first cat in the list.
	$categories = get_the_category();
	$cat = $categories[0]->term_id;

	if ( $echo )
		echo $cat;

	return $cat;
}

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Changelog

Changelog
Version Description
0.71 Introduced. Use get_the_category()