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function is not described

_navigation_markup() WP 4.1.0

Wraps passed links in navigational markup.

This is an internal function for using it by WP core itself. It's not recommended to use this function in your code.

Hooks from the function
Return

String. Navigation template tag.

Usage

_navigation_markup( $links, $class, $screen_reader_text, $aria_label );
$links(string) (required)
Navigational links.
$class(string)
Custom class for the nav element.
Default: 'posts-navigation'
$screen_reader_text(string)
Screen reader text for the nav element.
Default: 'Posts navigation'
$aria_label(string)
ARIA label for the nav element.
Default: value of $screen_reader_text

Changelog

Since 4.1.0 Introduced.
Since 5.3.0 Added the aria_label parameter.

Code of _navigation_markup() WP 5.7.2

<?php
function _navigation_markup( $links, $class = 'posts-navigation', $screen_reader_text = '', $aria_label = '' ) {
	if ( empty( $screen_reader_text ) ) {
		$screen_reader_text = __( 'Posts navigation' );
	}
	if ( empty( $aria_label ) ) {
		$aria_label = $screen_reader_text;
	}

	$template = '
	<nav class="navigation %1$s" role="navigation" aria-label="%4$s">
		<h2 class="screen-reader-text">%2$s</h2>
		<div class="nav-links">%3$s</div>
	</nav>';

	/**
	 * Filters the navigation markup template.
	 *
	 * Note: The filtered template HTML must contain specifiers for the navigation
	 * class (%1$s), the screen-reader-text value (%2$s), placement of the navigation
	 * links (%3$s), and ARIA label text if screen-reader-text does not fit that (%4$s):
	 *
	 *     <nav class="navigation %1$s" role="navigation" aria-label="%4$s">
	 *         <h2 class="screen-reader-text">%2$s</h2>
	 *         <div class="nav-links">%3$s</div>
	 *     </nav>
	 *
	 * @since 4.4.0
	 *
	 * @param string $template The default template.
	 * @param string $class    The class passed by the calling function.
	 * @return string Navigation template.
	 */
	$template = apply_filters( 'navigation_markup_template', $template, $class );

	return sprintf( $template, sanitize_html_class( $class ), esc_html( $screen_reader_text ), $links, esc_html( $aria_label ) );
}