<?php
/*
 *  Preprocess page.tpl.php to inject the $search_box variable back into D7.
 */
function MYTHEME_preprocess_page(&$variables){
  $search_box = drupal_render(drupal_get_form('search_form'));
  $variables['search_box'] = $search_box;
}
?>
Then you just need to print the variable in your page.tpl.php:
<?php print $search_box; ?>

adding drupal search in page.tpl in d7

drupal

PHP