Your problem is this line in your inc\incfiles\header.inc.php
<input name="q" type="text" size="60" placeholder="Search..."
You are missing the closing bracket -
<input name="q" type="text" size="60" placeholder="Search..." />
^^
because of that, the closing form tag on the next line is not beinging parsed, so your form in index.php
is being nestled inside the <form method="GET" action="search.php" id="search">