Solved PHP error when using site search

I have been getting an error whenever a search is done on my WordPress/Divi website. The results are listed, but there is an error listed first:

WARNING: USE OF UNDEFINED CONSTANT THEMENAME - ASSUMED 'THEMENAME' (THIS WILL THROW AN ERROR IN A FUTURE VERSION OF PHP) IN /path-to-the-theme/SEARCH.PHP ON LINE 17

Line 16-18 of the search.php file are as follows:

<header class="page-header">
<span class="search-page-title">
<?php printf( esc_html__( 'Search Results for: %s', themename ), '<span>' . get_search_query() . '</span>' ); ?></span>
</header><!-- .page-header -->

WordPress ver: 5.3.2
PHP ver: 7.3
Divi ver: 4.3.4 with a child theme

How do I fix this?

 

I had in my old code:

esc_html__( 'Search Results for: %s', themename )

The themename portion either should be a string literal 'themename' or more likely replaced with the folder name of your theme (themeslug). For example, when you installed the Twenty Twenty theme it's theme folder is twentytwenty and it's textdomain is 'twentytwenty'. A similar example in Twenty Twenty would look like this:

esc_html__( 'Search Results for: %s', 'twentytwenty' )

adding the quotes around the themename worked!