Any changes to functions.php causes errors

I’m using a code to make a ratings plugin appear in my custom taxonomy.
[code title=”functions.php”]
if ( $terms ) {
foreach ( $terms as $term ) {

if ( in_array( $term->name, array( ‘Services’, ‘Book Designing’, ‘Coaching and Consulting’,
‘Copywriting’, ‘Critiquing’, ‘Editing’, ‘Freelance Writing’, ‘Literary Agent’,
‘Marketing and Promoting’, ‘Proofreading’, ‘Publishing’ ) ) ) {
$found = true;
break;
}[/code]
It should appear in all the categories listed here, but I noticed that instead of “Literary Agents,” the plugin developer wrote “Literary Agent,” and so the ratings don’t show in that category. I simply added an “s” to the end, and I get this error on the front end:

Warning: Cannot modify header information – headers already sent by (output started at /home/curveson/public_html/wp-content/themes/template_New_Child_Theme_1/functions.php:1) in /home/curveson/public_html/wp-content/themes/BT/framework/class/class_layout.php on line 152

It doesn’t matter what I do in this file. The smallest of changes creates an error. Can someone help me with this? I have no idea how to change Agent to Agents without an error. I’d really appreciate some help. Thanks!