Function expects string but receiving array Warming??

I get the following warning which makes no sense to me. Warning: header() expects parameter 1 to be string, array given in /www/htdocs/jc/administration/edit_products/show_products.php on line 96 It's true that I am passing at an array to the function, but what I don't understand is why the function expects a string? How does any function know the type of an incoming var in PHP anyway? How can I fix my code to get rid of this error (while keeping the var as an array)?My code looks like this: header(array("ID","Name","Maker's Code","Maker Name","Label Name","Product Type")); function header_row($aH) { echo " <TR>"; foreach ($aH as $h) { ?>

    <TH>
      <?php echo $h; ?>
    </TH>

<?php } echo " </TR>"; }