在IIS上通过COM使用SAPI和PHP的问题

在过去,我已经使用此代码使TTS工作(Apache 2.1,PHP 5.5,在Windows 2003 Server上)

// Instantiate the object
$VoiceObj = new COM("SAPI.SpVoice") or die("Unable to instantiate SAPI");

// Get the available voices
$VoicesToken=$VoiceObj->GetVoices();
$NumberofVoices=$VoicesToken->Count;
for($i=0;$i<$NumberofVoices;$i++)
{
 $VoiceToken=$VoicesToken->Item($i);  
 $VoiceName[$i]=$VoiceToken->GetDescription();
}

// Get and print the id of the specified voice
$SelectedVoiceToken=$VoicesToken->Item(0);
$SelectedVoiceTokenid=$SelectedVoiceToken->id;

// Set the Voice
$VoiceObj->Voice=$SelectedVoiceToken;
$VoiceName=$VoiceObj->Voice->GetDescription();

$VoiceFile = new COM("SAPI.SpFileStream"); 
$VoiceFile->Open('./test.wav',3,false);


// Speak to file
$VoiceObj->AudioOutputStream = $VoiceFile;
$VoiceObj->Speak("What an unbelievable test",0);
$VoiceFile->Close();

在我的新设置(IIS 7.5,PHP 7.0,Windows Server 2008R2)上,相同的代码失败了

$VoiceObj->Speak("What an unbelievable test",0);

Fatal error: Uncaught com_exception: <b>Source:</b> Unknown<br/><b>Description:</b> Unknown in webtts.php:30 Stack trace: #0 webtts.php(30): com->Speak('this is a marve...',0) #1 {main}

有这么小的细节(在哪里检索更多？)我无法弄清楚问题可能是什么.

写入权限已检查.
PHP 7.0替换为5.5,仍然无法正常工作.
使用Win32应用程序测试相同的代码,它运行完美.

任何提示？