Source

File: wp-admin/includes/class-wp-screen.php

public function render_per_page_options() {
		if ( null === $this->get_option( 'per_page' ) ) {
			return;
		}

		$per_page_label = $this->get_option( 'per_page', 'label' );
		if ( null === $per_page_label ) {
			$per_page_label = __( 'Number of items per page:' );
		}

		$option = $this->get_option( 'per_page', 'option' );
		if ( ! $option ) {
			$option = str_replace( '-', '_', "{$this->id}_per_page" );
		}

		$per_page = (int) get_user_option( $option );
		if ( empty( $per_page ) || $per_page < 1 ) {
			$per_page = $this->get_option( 'per_page', 'default' );
			if ( ! $per_page ) {
				$per_page = 20;
			}
		}

		if ( 'edit_comments_per_page' === $option ) {
			$comment_status = isset( $_REQUEST['comment_status'] ) ? $_REQUEST['comment_status'] : 'all';

			/** This filter is documented in wp-admin/includes/class-wp-comments-list-table.php */
			$per_page = apply_filters( 'comments_per_page', $per_page, $comment_status );
		} elseif ( 'categories_per_page' === $option ) {
			/** This filter is documented in wp-admin/includes/class-wp-terms-list-table.php */
			$per_page = apply_filters( 'edit_categories_per_page', $per_page );
		} else {
			/** This filter is documented in wp-admin/includes/class-wp-list-table.php */
			$per_page = apply_filters( "{$option}", $per_page );
		}

		// Back compat.
		if ( isset( $this->post_type ) ) {
			/** This filter is documented in wp-admin/includes/post.php */
			$per_page = apply_filters( 'edit_posts_per_page', $per_page, $this->post_type );
		}

		// This needs a submit button.
		add_filter( 'screen_options_show_submit', '__return_true' );

		?>
		<fieldset class="screen-options">
		<legend><?php _e( 'Pagination' ); ?></legend>
			<?php if ( $per_page_label ) : ?>
				<label for="<?php echo esc_attr( $option ); ?>"><?php echo $per_page_label; ?></label>
				<input type="number" step="1" min="1" max="999" class="screen-per-page" name="wp_screen_options[value]"
					id="<?php echo esc_attr( $option ); ?>" maxlength="3"
					value="<?php echo esc_attr( $per_page ); ?>" />
			<?php endif; ?>
				<input type="hidden" name="wp_screen_options[option]" value="<?php echo esc_attr( $option ); ?>" />
		</fieldset>
		<?php
	}