WP_Query::parse_tax_query( array $q )

	public function parse_tax_query( &$q ) {
		if ( ! empty( $q['tax_query'] ) && is_array( $q['tax_query'] ) ) {
			$tax_query = $q['tax_query'];
		} else {
			$tax_query = array();
		}

		if ( !empty($q['taxonomy']) && !empty($q['term']) ) {
			$tax_query[] = array(
				'taxonomy' => $q['taxonomy'],
				'terms' => array( $q['term'] ),
				'field' => 'slug',
			);
		}

		foreach ( get_taxonomies( array() , 'objects' ) as $taxonomy => $t ) {
			if ( 'post_tag' == $taxonomy )
				continue;	// Handled further down in the $q['tag'] block

			if ( $t->query_var && !empty( $q[$t->query_var] ) ) {
				$tax_query_defaults = array(
					'taxonomy' => $taxonomy,
					'field' => 'slug',
				);

 				if ( isset( $t->rewrite['hierarchical'] ) && $t->rewrite['hierarchical'] ) {
					$q[$t->query_var] = wp_basename( $q[$t->query_var] );
				}

				$term = $q[$t->query_var];

				if ( is_array( $term ) ) {
					$term = implode( ',', $term );
				}

				if ( strpos($term, '+') !== false ) {
					$terms = preg_split( '/[+]+/', $term );
					foreach ( $terms as $term ) {
						$tax_query[] = array_merge( $tax_query_defaults, array(
							'terms' => array( $term )
						) );
					}
				} else {
					$tax_query[] = array_merge( $tax_query_defaults, array(
						'terms' => preg_split( '/[,]+/', $term )
					) );
				}
			}
		}

		// If querystring 'cat' is an array, implode it.
		if ( is_array( $q['cat'] ) ) {
			$q['cat'] = implode( ',', $q['cat'] );
		}

		// Category stuff
		if ( ! empty( $q['cat'] ) && ! $this->is_singular ) {
			$cat_in = $cat_not_in = array();

			$cat_array = preg_split( '/[,\s]+/', urldecode( $q['cat'] ) );
			$cat_array = array_map( 'intval', $cat_array );
			$q['cat'] = implode( ',', $cat_array );

			foreach ( $cat_array as $cat ) {
				if ( $cat > 0 )
					$cat_in[] = $cat;
				elseif ( $cat < 0 )
					$cat_not_in[] = abs( $cat );
			}

			if ( ! empty( $cat_in ) ) {
				$tax_query[] = array(
					'taxonomy' => 'category',
					'terms' => $cat_in,
					'field' => 'term_id',
					'include_children' => true
				);
			}

			if ( ! empty( $cat_not_in ) ) {
				$tax_query[] = array(
					'taxonomy' => 'category',
					'terms' => $cat_not_in,
					'field' => 'term_id',
					'operator' => 'NOT IN',
					'include_children' => true
				);
			}
			unset( $cat_array, $cat_in, $cat_not_in );
		}

		if ( ! empty( $q['category__and'] ) && 1 === count( (array) $q['category__and'] ) ) {
			$q['category__and'] = (array) $q['category__and'];
			if ( ! isset( $q['category__in'] ) )
				$q['category__in'] = array();
			$q['category__in'][] = absint( reset( $q['category__and'] ) );
			unset( $q['category__and'] );
		}

		if ( ! empty( $q['category__in'] ) ) {
			$q['category__in'] = array_map( 'absint', array_unique( (array) $q['category__in'] ) );
			$tax_query[] = array(
				'taxonomy' => 'category',
				'terms' => $q['category__in'],
				'field' => 'term_id',
				'include_children' => false
			);
		}

		if ( ! empty($q['category__not_in']) ) {
			$q['category__not_in'] = array_map( 'absint', array_unique( (array) $q['category__not_in'] ) );
			$tax_query[] = array(
				'taxonomy' => 'category',
				'terms' => $q['category__not_in'],
				'operator' => 'NOT IN',
				'include_children' => false
			);
		}

		if ( ! empty($q['category__and']) ) {
			$q['category__and'] = array_map( 'absint', array_unique( (array) $q['category__and'] ) );
			$tax_query[] = array(
				'taxonomy' => 'category',
				'terms' => $q['category__and'],
				'field' => 'term_id',
				'operator' => 'AND',
				'include_children' => false
			);
		}

		// If querystring 'tag' is array, implode it.
		if ( is_array( $q['tag'] ) ) {
			$q['tag'] = implode( ',', $q['tag'] );
		}

		// Tag stuff
		if ( '' != $q['tag'] && !$this->is_singular && $this->query_vars_changed ) {
			if ( strpos($q['tag'], ',') !== false ) {
				$tags = preg_split('/[,\r\n\t ]+/', $q['tag']);
				foreach ( (array) $tags as $tag ) {
					$tag = sanitize_term_field('slug', $tag, 0, 'post_tag', 'db');
					$q['tag_slug__in'][] = $tag;
				}
			} elseif ( preg_match('/[+\r\n\t ]+/', $q['tag'] ) || ! empty( $q['cat'] ) ) {
				$tags = preg_split('/[+\r\n\t ]+/', $q['tag']);
				foreach ( (array) $tags as $tag ) {
					$tag = sanitize_term_field('slug', $tag, 0, 'post_tag', 'db');
					$q['tag_slug__and'][] = $tag;
				}
			} else {
				$q['tag'] = sanitize_term_field('slug', $q['tag'], 0, 'post_tag', 'db');
				$q['tag_slug__in'][] = $q['tag'];
			}
		}

		if ( !empty($q['tag_id']) ) {
			$q['tag_id'] = absint( $q['tag_id'] );
			$tax_query[] = array(
				'taxonomy' => 'post_tag',
				'terms' => $q['tag_id']
			);
		}

		if ( !empty($q['tag__in']) ) {
			$q['tag__in'] = array_map('absint', array_unique( (array) $q['tag__in'] ) );
			$tax_query[] = array(
				'taxonomy' => 'post_tag',
				'terms' => $q['tag__in']
			);
		}

		if ( !empty($q['tag__not_in']) ) {
			$q['tag__not_in'] = array_map('absint', array_unique( (array) $q['tag__not_in'] ) );
			$tax_query[] = array(
				'taxonomy' => 'post_tag',
				'terms' => $q['tag__not_in'],
				'operator' => 'NOT IN'
			);
		}

		if ( !empty($q['tag__and']) ) {
			$q['tag__and'] = array_map('absint', array_unique( (array) $q['tag__and'] ) );
			$tax_query[] = array(
				'taxonomy' => 'post_tag',
				'terms' => $q['tag__and'],
				'operator' => 'AND'
			);
		}

		if ( !empty($q['tag_slug__in']) ) {
			$q['tag_slug__in'] = array_map('sanitize_title_for_query', array_unique( (array) $q['tag_slug__in'] ) );
			$tax_query[] = array(
				'taxonomy' => 'post_tag',
				'terms' => $q['tag_slug__in'],
				'field' => 'slug'
			);
		}

		if ( !empty($q['tag_slug__and']) ) {
			$q['tag_slug__and'] = array_map('sanitize_title_for_query', array_unique( (array) $q['tag_slug__and'] ) );
			$tax_query[] = array(
				'taxonomy' => 'post_tag',
				'terms' => $q['tag_slug__and'],
				'field' => 'slug',
				'operator' => 'AND'
			);
		}

		$this->tax_query = new WP_Tax_Query( $tax_query );

		/**
		 * Fires after taxonomy-related query vars have been parsed.
		 *
		 * @since WP-3.7.0
		 *
		 * @param WP_Query $this The WP_Query instance.
		 */
		do_action( 'parse_tax_query', $this );
	}