You should use a parameter instead of an integer value, not inside quotation marks.
1: LIKE :
$result = pg_query_params ( $dbconn,
"SELECT question_id, body
FROM questions
WHERE body ilike $1",
array ( "%" . $_GET['search'] . "%")
);
2: LIKE SQL:
$result = pg_query_params ( $dbconn,
"SELECT question_id, body
FROM questions
WHERE body ilike '%' || $1 || '%'",
array ( $_GET['search'] )
);