Use theme hook suggestion in drupal

If you want to Drupal to use some specific template based on some name, then you have to write theme hook suggestion.

Through which you can mention your custom template file that will used by Drupal instead of page.tpl.php or some other template file.

Here is the code :

function THEME_preprocess_page(&$variables) {
  if (isset($variables['node']->type)) {
   // If the content type's machine name is "my_machine_name" the file
   // name will be "page--my-machine-name.tpl.php".
   $variables['theme_hook_suggestions'][] = 'page__' . $variables['node']->type;
   }
}