[WordPress] Adding attributes to single post pagination links.

single-post-pagination-link-attributes.php

<?php

/**
 * Adds the title attribute to the 'Next and 'Previous' post pagination anchors.
 *
 * @param       string     $link    The anchor element for the next or previous post.
 * @return	string              The pagination link with the additional attribute.
 */
function acme_add_title_to_single_post_pagination( $link ) {

	if ( 0 < strpos( $link, 'rel="prev"' ) ) {

		$previous_post = get_previous_post();
		$link = str_replace( 'rel="prev"', 'rel="prev" title="' . esc_attr( get_the_title( $previous_post->ID ) ) . '"', $link );

	} else {

		$next_post = get_next_post();
		$link = str_replace( 'rel="next"', 'rel="next" title="' . esc_attr( get_the_title( $next_post->ID ) ) . '"', $link );

	} // end if/else

	return $link;

} // end acme_add_title_to_single_post_pagination
add_filter( 'next_post_link', 'acme_add_title_to_single_post_pagination' );
add_filter( 'previous_post_link', 'acme_add_title_to_single_post_pagination' );