wp-includes/deprecated.php:84Returns or prints a category ID.
$displaybooloptionaltrueintfunction the_category_ID($display = true) { _deprecated_function( __FUNCTION__, '0.71', 'get_the_category()' ); // Grab the first cat in the list. $categories = get_the_category(); $cat = $categories[0]->term_id; if ( $display ) echo $cat; return $cat;}Introduced in 0.71. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/deprecated.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.