wp_generate_tag_cloud( WP_Term[] $tags, string|array $args = '' )

function wp_generate_tag_cloud( $tags, $args = '' ) {
	$defaults = array(
		'smallest' => 8, 'largest' => 22, 'unit' => 'pt', 'number' => 0,
		'format' => 'flat', 'separator' => "\n", 'orderby' => 'name', 'order' => 'ASC',
		'topic_count_text' => null, 'topic_count_text_callback' => null,
		'topic_count_scale_callback' => 'default_topic_count_scale', 'filter' => 1,
		'show_count' => 0,
	);

	$args = wp_parse_args( $args, $defaults );

	$return = ( 'array' === $args['format'] ) ? array() : '';

	if ( empty( $tags ) ) {
		return $return;
	}

	// Juggle topic counts.
	if ( isset( $args['topic_count_text'] ) ) {
		// First look for nooped plural support via topic_count_text.
		$translate_nooped_plural = $args['topic_count_text'];
	} elseif ( ! empty( $args['topic_count_text_callback'] ) ) {
		// Look for the alternative callback style. Ignore the previous default.
		if ( $args['topic_count_text_callback'] === 'default_topic_count_text' ) {
			$translate_nooped_plural = _n_noop( '%s item', '%s items' );
		} else {
			$translate_nooped_plural = false;
		}
	} elseif ( isset( $args['single_text'] ) && isset( $args['multiple_text'] ) ) {
		// If no callback exists, look for the old-style single_text and multiple_text arguments.
		$translate_nooped_plural = _n_noop( $args['single_text'], $args['multiple_text'] );
	} else {
		// This is the default for when no callback, plural, or argument is passed in.
		$translate_nooped_plural = _n_noop( '%s item', '%s items' );
	}

	/**
	 * Filters how the items in a tag cloud are sorted.
	 *
	 * @since WP-2.8.0
	 *
	 * @param array $tags Ordered array of terms.
	 * @param array $args An array of tag cloud arguments.
	 */
	$tags_sorted = apply_filters( 'tag_cloud_sort', $tags, $args );
	if ( empty( $tags_sorted ) ) {
		return $return;
	}

	if ( $tags_sorted !== $tags ) {
		$tags = $tags_sorted;
		unset( $tags_sorted );
	} else {
		if ( 'RAND' === $args['order'] ) {
			shuffle( $tags );
		} else {
			// SQL cannot save you; this is a second (potentially different) sort on a subset of data.
			if ( 'name' === $args['orderby'] ) {
				uasort( $tags, '_wp_object_name_sort_cb' );
			} else {
				uasort( $tags, '_wp_object_count_sort_cb' );
			}

			if ( 'DESC' === $args['order'] ) {
				$tags = array_reverse( $tags, true );
			}
		}
	}

	if ( $args['number'] > 0 )
		$tags = array_slice( $tags, 0, $args['number'] );

	$counts = array();
	$real_counts = array(); // For the alt tag
	foreach ( (array) $tags as $key => $tag ) {
		$real_counts[ $key ] = $tag->count;
		$counts[ $key ] = call_user_func( $args['topic_count_scale_callback'], $tag->count );
	}

	$min_count = min( $counts );
	$spread = max( $counts ) - $min_count;
	if ( $spread <= 0 )
		$spread = 1;
	$font_spread = $args['largest'] - $args['smallest'];
	if ( $font_spread < 0 )
		$font_spread = 1;
	$font_step = $font_spread / $spread;

	$aria_label = false;
	/*
	 * Determine whether to output an 'aria-label' attribute with the tag name and count.
	 * When tags have a different font size, they visually convey an important information
	 * that should be available to assistive technologies too. On the other hand, sometimes
	 * themes set up the Tag Cloud to display all tags with the same font size (setting
	 * the 'smallest' and 'largest' arguments to the same value).
	 * In order to always serve the same content to all users, the 'aria-label' gets printed out:
	 * - when tags have a different size
	 * - when the tag count is displayed (for example when users check the checkbox in the
	 *   Tag Cloud widget), regardless of the tags font size
	 */
	if ( $args['show_count'] || 0 !== $font_spread ) {
		$aria_label = true;
	}

	// Assemble the data that will be used to generate the tag cloud markup.
	$tags_data = array();
	foreach ( $tags as $key => $tag ) {
		$tag_id = isset( $tag->id ) ? $tag->id : $key;

		$count = $counts[ $key ];
		$real_count = $real_counts[ $key ];

		if ( $translate_nooped_plural ) {
			$formatted_count = sprintf( translate_nooped_plural( $translate_nooped_plural, $real_count ), number_format_i18n( $real_count ) );
		} else {
			$formatted_count = call_user_func( $args['topic_count_text_callback'], $real_count, $tag, $args );
		}

		$tags_data[] = array(
			'id'              => $tag_id,
			'url'             => '#' != $tag->link ? $tag->link : '#',
			'role'            => '#' != $tag->link ? '' : ' role="button"',
			'name'            => $tag->name,
			'formatted_count' => $formatted_count,
			'slug'            => $tag->slug,
			'real_count'      => $real_count,
			'class'           => 'tag-cloud-link tag-link-' . $tag_id,
			'font_size'       => $args['smallest'] + ( $count - $min_count ) * $font_step,
			'aria_label'      => $aria_label ? sprintf( ' aria-label="%1$s (%2$s)"', esc_attr( $tag->name ), esc_attr( $formatted_count ) ) : '',
			'show_count'      => $args['show_count'] ? '<span class="tag-link-count"> (' . $real_count . ')</span>' : '',
		);
	}

	/**
	 * Filters the data used to generate the tag cloud.
	 *
	 * @since WP-4.3.0
	 *
	 * @param array $tags_data An array of term data for term used to generate the tag cloud.
	 */
	$tags_data = apply_filters( 'wp_generate_tag_cloud_data', $tags_data );

	$a = array();

	// Generate the output links array.
	foreach ( $tags_data as $key => $tag_data ) {
		$class = $tag_data['class'] . ' tag-link-position-' . ( $key + 1 );
		$a[] = sprintf(
			'<a href="%1$s"%2$s class="%3$s" style="font-size: %4$s;"%5$s>%6$s%7$s</a>',
			esc_url( $tag_data['url'] ),
			$tag_data['role'],
			esc_attr( $class ),
			esc_attr( str_replace( ',', '.', $tag_data['font_size'] ) . $args['unit'] ),
			$tag_data['aria_label'],
			esc_html( $tag_data['name'] ),
			$tag_data['show_count']
		);
	}

	switch ( $args['format'] ) {
		case 'array' :
			$return =& $a;
			break;
		case 'list' :
			/*
			 * Force role="list", as some browsers (sic: Safari 10) don't expose to assistive
			 * technologies the default role when the list is styled with `list-style: none`.
			 * Note: this is redundant but doesn't harm.
			 */
			$return = "<ul class='wp-tag-cloud' role='list'>\n\t<li>";
			$return .= join( "</li>\n\t<li>", $a );
			$return .= "</li>\n</ul>\n";
			break;
		default :
			$return = join( $args['separator'], $a );
			break;
	}

	if ( $args['filter'] ) {
		/**
		 * Filters the generated output of a tag cloud.
		 *
		 * The filter is only evaluated if a true value is passed
		 * to the $filter argument in wp_generate_tag_cloud().
		 *
		 * @since WP-2.3.0
		 *
		 * @see wp_generate_tag_cloud()
		 *
		 * @param array|string $return String containing the generated HTML tag cloud output
		 *                             or an array of tag links if the 'format' argument
		 *                             equals 'array'.
		 * @param array        $tags   An array of terms used in the tag cloud.
		 * @param array        $args   An array of wp_generate_tag_cloud() arguments.
		 */
		return apply_filters( 'wp_generate_tag_cloud', $return, $tags, $args );
	}

	else
		return $return;
}