xmlrpc_getpostcategory( string $content )

Source

File: wp-includes/functions.php

function xmlrpc_getpostcategory( $content ) {
	global $post_default_category;
	if ( preg_match( '/<category>(.+?)<\/category>/is', $content, $matchcat ) ) {
		$post_category = trim( $matchcat[1], ',' );
		$post_category = explode( ',', $post_category );
	} else {
		$post_category = $post_default_category;
	}
	return $post_category;
}