Walker_Category::start_el( string $output, WP_Term $data_object, int $depth = 0, array $args = array(), int $current_object_id = 0 )

Compatibility

Present in every tracked release (6.7.7 to 7.1.0), and compiles on PHP 7.4 through 8.6-dev.

Parameters

$outputstring

Used to append additional content (passed by reference).

$data_objectWP_Term

Category data object.

$depthintoptional

Depth of category in reference to parents. Default 0.Default: 0

$argsarrayoptional

An array of arguments. See wp_list_categories().
Default empty array.Default: array()

$current_object_idintoptional

ID of the current category. Default 0.Default: 0

Performance profile

How much work a call to Walker_Category::start_el() does, and what it touches: the algorithmic scaling, the Zend instruction count per call across PHP versions, the hooks it hands control to, and the core code that calls it. Measured from the compiled opcodes, not a stopwatch, so every number is identical on any machine running the same PHP version, and every function in core is ranked by cost.

Cost class

Heavy

Reaches the database via get_terms().

Scaling

Scales with input

The body loops, so the work grows with what you pass in.

Instructions

60–166

Executed per call on PHP 8.5, depending on the branch taken. The body compiles to 255.

Plugin surface

4 hooks

Third-party callbacks on 'list_cats', 'category_description', 'category_list_link_attributes' run inside this call, and their cost is not bounded by anything here.

Called by

0

Nothing in core calls this; the cost is only what you spend yourself.

What it touches

• hookthird-party callbacksapply_filters()called directly
• querycontent queryget_terms()called directly
• optionoption read or writeget_option()one call below Walker_Category::start_el()

Further down the call graph this can also reach cache, serialize and transient. Those are the worst case, several calls deep and usually down an error path, not what a normal call pays.

What one call costs · 100 distinct outcomes

One number would be a lie: the work depends on which branch runs. These are every distinct cost Walker_Category::start_el() can have, taken from its control-flow graph on PHP 8.5.

This body has more branch combinations than are worth enumerating, so the table covers the outcomes found first rather than every one that exists.

Hooks and filters fired · 4

4 hooks fire while Walker_Category::start_el() runs, in this order:

1. 1
   apply_filters( list_cats )filterline 106 (+5 into the body)

   Filters a taxonomy drop-down display element.

2. 2
   apply_filters( category_description )filterline 125 (+24 into the body)

   Filters the category description for display.

3. 3
   apply_filters( category_list_link_attributes )filterline 144 (+43 into the body)

   Filters the HTML attributes applied to a category list item's anchor element.

4. 4
   apply_filters( category_css_class )filterline 245 (+144 into the body)

   Filters the list of CSS classes to include with each category in the list.

Uses · 9

• apply_filters()Calls the callback functions that have been added to a filter hook.
• esc_attr()Escaping for HTML attributes.
• get_term_link()Generates a permalink for a taxonomy term archive.
• esc_url()Checks and cleans a URL.
• get_term_feed_link()Retrieves the feed link for a term.
• __()Retrieves the translation of $text.
• number_format_i18n()Converts float number to format based on the locale.
• get_terms()Retrieves the terms in a given taxonomy or list of taxonomies.
• get_term()Gets all term data from database by term ID.

Source code

View on Trac ↗View on GitHub ↗

101	public function start_el( &$output, $data_object, $depth = 0, $args = array(), $current_object_id = 0 ) {102		// Restores the more descriptive, specific name for use within this method.103		$category = $data_object;104 105		/** This filter is documented in wp-includes/category-template.php */106		$cat_name = apply_filters( 'list_cats', esc_attr( $category->name ), $category );107 108		// Don't generate an element if the category name is empty.109		if ( '' === $cat_name ) {110			return;111		}112 113		$atts         = array();114		$atts['href'] = get_term_link( $category );115 116		if ( $args['use_desc_for_title'] && ! empty( $category->description ) ) {117			/**118			 * Filters the category description for display.119			 *120			 * @since 1.2.0121			 *122			 * @param string  $description Category description.123			 * @param WP_Term $category    Category object.124			 */125			$atts['title'] = strip_tags( apply_filters( 'category_description', $category->description, $category ) );126		}127 128		/**129		 * Filters the HTML attributes applied to a category list item's anchor element.130		 *131		 * @since 5.2.0132		 *133		 * @param array   $atts {134		 *     The HTML attributes applied to the list item's `<a>` element, empty strings are ignored.135		 *136		 *     @type string $href  The href attribute.137		 *     @type string $title The title attribute.138		 * }139		 * @param WP_Term $category          Term data object.140		 * @param int     $depth             Depth of category, used for padding.141		 * @param array   $args              An array of arguments.142		 * @param int     $current_object_id ID of the current category.143		 */144		$atts = apply_filters( 'category_list_link_attributes', $atts, $category, $depth, $args, $current_object_id );145 146		$attributes = '';147		foreach ( $atts as $attr => $value ) {148			if ( is_scalar( $value ) && '' !== $value && false !== $value ) {149				$value       = ( 'href' === $attr ) ? esc_url( $value ) : esc_attr( $value );150				$attributes .= ' ' . $attr . '="' . $value . '"';151			}152		}153 154		$link = sprintf(155			'<a%s>%s</a>',156			$attributes,157			$cat_name158		);159 160		if ( ! empty( $args['feed_image'] ) || ! empty( $args['feed'] ) ) {161			$link .= ' ';162 163			if ( empty( $args['feed_image'] ) ) {164				$link .= '(';165			}166 167			$link .= '<a href="' . esc_url( get_term_feed_link( $category, $category->taxonomy, $args['feed_type'] ) ) . '"';168 169			if ( empty( $args['feed'] ) ) {170				/* translators: %s: Category name. */171				$alt = ' alt="' . sprintf( __( 'Feed for all posts filed under %s' ), $cat_name ) . '"';172			} else {173				$alt   = ' alt="' . $args['feed'] . '"';174				$name  = $args['feed'];175				$link .= empty( $args['title'] ) ? '' : $args['title'];176			}177 178			$link .= '>';179 180			if ( empty( $args['feed_image'] ) ) {

Changelog

Introduced in 2.1.0. Unchanged from 6.7.7 through 7.1.0.

1. 6.7.7
2. 6.8.8
3. 6.9.7
4. 7.0.4
5. 7.1.0

Signature, return type and hooks compared across 5 parsed releases.

About this page

Parsed data

Generated from the wordpress-develop 7.1.0 tag, from src/wp-includes/class-walker-category.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.

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