You can use include(), require() or include_once() functions to include other pages in your PHP code, you can also escape from PHP (using <?php ?>) and print your HTML withous using print(), for example:
if(!foo()) {
?>
--- HTML STUFF ---
<?php
}
?>
People do print() and echo() generaly 'cos they want to use PHP variables set before in the HTML, for example:
while($row=mysql_fecth_array($result)) {
echo "<a ref=$row[link]>$row[name]</a>";
}
regards
Anderson