get_post_meta Returns an Empty Array inside a Function

In a function with a form that grabs a string, the following code prints an array containing the comma-separated data in that string:

$locations_string = esc_html( get_post_meta( $item_id, 'locations', true ) );
$locations_array = explode(',', $locations_string);
$locations_array_trimmed = array_map('trim', $locations_array);
Print_r($locations_array_trimmed);

and the variable ‘locations’ is saved to the database.

However, the code prints an empty array in a function further down the page. Any ideas why this might be?