blank page of PHP script

[aix tiger]

Guys
   
  I am using latest version of mysql, PHP and Apache 2 on RHEL 4.
   
  Every thing is working fine , even simple php pages are being displayed correctly , howvere , when i load some PHP script files , page remain blank and nothing being executed on server side.
   
  Here is the code of php file :
   
  <?php
//define("PB_CRYPT_LINKS" , 1);
define("_LIBPATH","./lib/");
require_once _LIBPATH . "site.php";
  $site = new CSite("./site.xml",true);
$site->Run();
?>

  No errors appear in access logs or error logs of httpd server.Only blank page appears although i was expecting to execute some configuration execution for a software ( a help desk software).
   
  Instead , if i put following PHP file , i get expected outcome while accessing that file through my browser.
   
  <?php
$Cat = "Spot";
$Dog = "Clif";
Print "My cat " . $Cat . " and my dog " . $Dog . " like to play together.";
?>

  Can anybody help me on this issue ; as i beleive that there is nothing wrong in the code itself as same problem happening to another open source configuration installtaion script ( which is also based on php).
   
  Regards
   
  Khurram
   
   
   

 
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