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<?php

/**
 * reindex after adding or updating this filter
 */
add_filter( 'facetwp_index_row', function( $params, $class ) {
	if ( 'my_facet' == $params['facet_name'] ) { // change my_facet to your facet's name/slug
		if ( '1' == $params['facet_value'] ) { // be careful with 1 and 0 as values - https://www.php.net/manual/en/types.comparisons.php
		    $params['facet_display_value'] = 'My Label'; // text to display in the facet choices
        	}
	}
	return $params;
}, 10, 2 );