php com word to html,PHP Convert word to html with COM

$file='C:/a.doc';

$saveas=__DIR__.'/tmp/a.html';

$word=new COM('word.application');

$document=$word->Documents->Open($file);

$document->SaveAs($saveas,8);

$word->Quit();

$word=null;

echo file_get_contents($saveas);

@unlink($saveas);

It works fine in PHP CLI mode(php -f "com_server.php"), but when I run it through web(windows/apache http://localhost/com_server.php), an error occurred:

Fatal error: Uncaught exception 'com_exception' with message 'Failed

to create COM object `word.application': Server execution failed' in

D:\www\wwwroot\com_server.php:16 Stack trace: #0

D:\www\wwwroot\com_server.php(16): com->com('word.applicatio...') #1

{main} thrown in D:\www\wwwroot\com_server.php on line 16

I've also tried to wrap the code in shell_exec, but same error as well.

Any suggestions?