WordPress/wp-includes/blocks/query-pagination-previous.php

<?php
/**
 * Server-side rendering of the `core/query-pagination-previous` block.
 *
 * @package WordPress
 */

/**
 * Renders the `core/query-pagination-previous` block on the server.
 *
 * @param array    $attributes Block attributes.
 * @param string   $content    Block default content.
 * @param WP_Block $block      Block instance.
 *
 * @return string Returns the previous posts link for the query.
 */
function render_block_core_query_pagination_previous( $attributes, $content, $block ) {
	$page_key = isset( $block->context['queryId'] ) ? 'query-' . $block->context['queryId'] . '-page' : 'query-page';
	$page     = empty( $_GET[ $page_key ] ) ? 1 : (int) $_GET[ $page_key ];

	$wrapper_attributes = get_block_wrapper_attributes();
	$show_label         = isset( $block->context['showLabel'] ) ? (bool) $block->context['showLabel'] : true;
	$default_label      = __( 'Previous Page' );
	$label_text         = isset( $attributes['label'] ) && ! empty( $attributes['label'] ) ? esc_html( $attributes['label'] ) : $default_label;
	$label              = $show_label ? $label_text : '';
	$pagination_arrow   = get_query_pagination_arrow( $block, false );
	if ( ! $label ) {
		$wrapper_attributes .= ' aria-label="' . $label_text . '"';
	}
	if ( $pagination_arrow ) {
		$label = $pagination_arrow . $label;
	}
	$content = '';
	// Check if the pagination is for Query that inherits the global context
	// and handle appropriately.
	if ( isset( $block->context['query']['inherit'] ) && $block->context['query']['inherit'] ) {
		$filter_link_attributes = static function() use ( $wrapper_attributes ) {
			return $wrapper_attributes;
		};

		add_filter( 'previous_posts_link_attributes', $filter_link_attributes );
		$content = get_previous_posts_link( $label );
		remove_filter( 'previous_posts_link_attributes', $filter_link_attributes );
	} elseif ( 1 !== $page ) {
		$content = sprintf(
			'<a href="%1$s" %2$s>%3$s</a>',
			esc_url( add_query_arg( $page_key, $page - 1 ) ),
			$wrapper_attributes,
			$label
		);
	}
	return $content;
}

/**
 * Registers the `core/query-pagination-previous` block on the server.
 */
function register_block_core_query_pagination_previous() {
	register_block_type_from_metadata(
		__DIR__ . '/query-pagination-previous',
		array(
			'render_callback' => 'render_block_core_query_pagination_previous',
		)
	);
}
add_action( 'init', 'register_block_core_query_pagination_previous' );