Use this function instead. Then put the_excerpt();
in your template.
/**
* Find the last period in the excerpt and remove everything after it.
* If no period is found, just return the entire excerpt.
*
* @param string $excerpt The post excerpt.
*/
function end_with_sentence( $excerpt ) {
if ( ( $pos = mb_strrpos( $excerpt, '.' ) ) !== false ) {
$excerpt = substr( $excerpt, 0, $pos + 1 );
}
return $excerpt;
}
add_filter( 'the_excerpt', 'end_with_sentence' );