Get taxonomy by term and keep it in transient

gistfile1.txt

public function get_tax_by_term($use_var) {

		if ( ! $this->all_terms ) {
			$this->all_terms = get_transient('all_terms_' . $this->post_type );
			if ( ! $this->all_terms ) {
				$taxonomy_names = get_object_taxonomies( $this->post_type );
				$this->all_terms = [];
				foreach ( $taxonomy_names as $taxonomy_name ) {
					$terms                       = get_terms( [
						'taxonomy'   => $taxonomy_name,
						'hide_empty' => false,
						'fields'     => 'id=>slug',
					] );
					$this->all_terms[ $taxonomy_name ] = $terms;
				}
				set_transient('all_terms_' . $this->post_type, $this->all_terms, DAY_IN_SECONDS );
			}
		}

		$tax = array_filter( $this->all_terms, function($element, $key) use ($use_var) {
			if ( in_array( $use_var, $element ) ) {
				return true;
			}
			return null;
		}, ARRAY_FILTER_USE_BOTH );

		return $tax ? array_key_first($tax) : null;
	}